https://wiki.restarters.net/index.php?title=Digital_weighing_scales&feed=atom&action=historyDigital weighing scales - Revision history2024-03-29T06:37:51ZRevision history for this page on the wikiMediaWiki 1.38.2https://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=10747&oldid=prevPhilip: /* External links */2024-03-26T21:12:41Z<p><span dir="auto"><span class="autocomment">External links</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==External links==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==External links==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>* [https://learn.sparkfun.com/tutorials/getting-started-with-load-cells Getting Stated with Load Cells].</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
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<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[https://www.ifixit.com/Device/Kitchen_Scale iFixit]</ins></div></td></tr>
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<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>* [https://learn.sparkfun.com/tutorials/getting-started-with-load-cells Getting Stated with Load Cells] <ins style="font-weight: bold; text-decoration: none;">at Sparkfun</ins>.</div></td></tr>
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</table>Philiphttps://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=9951&oldid=prevPhilip: /* Half Bridge Load Cells */2023-06-08T20:30:48Z<p><span dir="auto"><span class="autocomment">Half Bridge Load Cells</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Half Bridge Load Cells===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Half Bridge Load Cells===</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Img_1727a.jpg|180px|thumb|left|A half-bridge load cell - top.]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Img_1727a.jpg|180px|thumb|left|A half-bridge load cell - top.]]</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[File:Img_1728a.jpg|180px|thumb|<del style="font-weight: bold; text-decoration: none;">right</del>|A half-bridge load cell - bottom.]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[File:DoubleBridge.png|180px|thumb|right|Four half bridge load cells in a full bridge configuration.]]</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File:Img_1728a.jpg|180px|thumb|<ins style="font-weight: bold; text-decoration: none;">left</ins>|A half-bridge load cell - bottom.]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The bar-type load cells contain 4 strain gauges in a "full bridge" configuration and has 4 wires, but bathroom scales commonly use 4 load cells, each with only 3 wires and each containing just 2 strain gauges at either end of a strip of metal. These are known as "half-bridge" load cells.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The bar-type load cells contain 4 strain gauges in a "full bridge" configuration and has 4 wires, but bathroom scales commonly use 4 load cells, each with only 3 wires and each containing just 2 strain gauges at either end of a strip of metal. These are known as "half-bridge" load cells.</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>These are still wired in a Wheatstone bridge, but each of the 4 arms of the bridge contains 2 strain gauges, one from each of 2 adjacent load cells stressed in the same sense, as shown in the diagram. The total imbalance of the Wheatstone bridge is then the sum of the imbalances of the 4 load cells, whether or not the load is evenly distributed amongst them.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>These are still wired in a Wheatstone bridge, but each of the 4 arms of the bridge contains 2 strain gauges, one from each of 2 adjacent load cells stressed in the same sense, as shown in the diagram. The total imbalance of the Wheatstone bridge is then the sum of the imbalances of the 4 load cells, whether or not the load is evenly distributed amongst them.</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">[[File:DoubleBridge.png|180px|thumb|right|Four half bridge load cells in a full bridge configuration.]]</del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>=Fault-finding and Repair=</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>=Fault-finding and Repair=</div></td></tr>
</table>Philiphttps://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=9949&oldid=prevPhilip at 20:58, 6 June 20232023-06-06T20:58:44Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Check there is nothing obstructing the load cell or cells and their wires aren't broken. The wires are often quite thin. The wires should be routed neatly from the load cell or load cells to the circuit board, ideally, lightly twisted together. If excessively long and loosely routed it is possible that nearby mains wiring could induce currents which could cause inaccurate or inconsistent readings.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Check there is nothing obstructing the load cell or cells and their wires aren't broken. The wires are often quite thin. The wires should be routed neatly from the load cell or load cells to the circuit board, ideally, lightly twisted together. If excessively long and loosely routed it is possible that nearby mains wiring could induce currents which could cause inaccurate or inconsistent readings.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Missing rows of pixels on the display can be caused by poor contact between the LCD and the circuit board it's mounted on. Sometimes the connection is made by a strip of [[<del style="font-weight: bold; text-decoration: none;">Connectors</del>#Elastomeric_.28or_ZEBRA.29_connectors|conductive rubber]] which only conducts across its width and not along its length. If you can somehow increase the pressure or clean both the circuit board and the contact area of the LCD you may be able to improve it.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Missing rows of pixels on the display can be caused by poor contact between the LCD and the circuit board it's mounted on. Sometimes the connection is made by a strip of [[<ins style="font-weight: bold; text-decoration: none;">Connectors_(Internal)</ins>#Elastomeric_.28or_ZEBRA.29_connectors|conductive rubber]] which only conducts across its width and not along its length. If you can somehow increase the pressure or clean both the circuit board and the contact area of the LCD you may be able to improve it.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Push buttons can become unreliable with use. Often, the button on the control panel is simply a piece of plastic which actuates a [[Passive_components#Switches and Push-Buttons|tactile push button switch]] underneath. These are readily available in a range of fairly standard sizes.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Push buttons can become unreliable with use. Often, the button on the control panel is simply a piece of plastic which actuates a [[Passive_components#Switches and Push-Buttons|tactile push button switch]] underneath. These are readily available in a range of fairly standard sizes.</div></td></tr>
</table>Philiphttps://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=9662&oldid=prevPhilip: /* Identifying load cell connections */2023-05-13T16:56:07Z<p><span dir="auto"><span class="autocomment">Identifying load cell connections</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 16:56, 13 May 2023</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l55">Line 55:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Should you need to identify the connections to a load cell (for example if 2 or more are broken) you can do so quite easily with a [[Glossary:Multimeter|multimeter]] on a 2kΩ [[Glossary:Resistance|resistance]] range.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Should you need to identify the connections to a load cell (for example if 2 or more are broken) you can do so quite easily with a [[Glossary:Multimeter|multimeter]] on a 2kΩ [[Glossary:Resistance|resistance]] range.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>For a half-bridge load cell (3 wires only), this contains just 2 strain gauges. Find one wire that measures the same resistance to either of the other two. This is the centre point of the two strain gauges, and the resistance between those other two should read twice as much. Wiring 4 such load cells into a [[Digital_weighing_scales#Wheatstone_Bridge_Connection|Wheatstone bridge]], the 4 centre points are the + and - inputs, and the two outputs. <del style="font-weight: bold; text-decoration: none;">Th </del>other wires are all connected in pairs of the same colour (see the diagram earlier).</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>For a half-bridge load cell (3 wires only), this contains just 2 strain gauges. Find one wire that measures the same resistance to either of the other two. This is the centre point of the two strain gauges, and the resistance between those other two should read twice as much. Wiring 4 such load cells into a [[Digital_weighing_scales#Wheatstone_Bridge_Connection|Wheatstone bridge]], the 4 centre points are the + and - inputs, and the two outputs. <ins style="font-weight: bold; text-decoration: none;">The </ins>other wires are all connected in pairs of the same colour (see the diagram earlier).</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A full bridge load cell has 4 wires and contains 4 strain gauges in a Wheatstone bridge. Measure the resistance from any one wire to each of the other three in turn. One should measure more than the other two, to be precise, two and two thirds as much. This is the opposite corner of the bridge. It doesn't matter which pair of corners you use as + and - inputs and which as outputs, but if the scales give negative weights, just swap the two wires of one pair.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A full bridge load cell has 4 wires and contains 4 strain gauges in a Wheatstone bridge. Measure the resistance from any one wire to each of the other three in turn. One should measure more than the other two, to be precise, two and two thirds as much. This is the opposite corner of the bridge. It doesn't matter which pair of corners you use as + and - inputs and which as outputs, but if the scales give negative weights, just swap the two wires of one pair.</div></td></tr>
</table>Philiphttps://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=6730&oldid=prevPhilip at 10:05, 15 October 20222022-10-15T10:05:12Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 10:05, 15 October 2022</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1">Line 1:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This page covers digital kitchen and bathroom scales. Digital luggage scales follow the same principles of operation.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This page covers digital kitchen and bathroom scales. Digital luggage scales follow the same principles of operation.</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"><div class="showtoc"></ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">__TOC__</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></div></ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Summary==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Summary==</div></td></tr>
</table>Philiphttps://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=6499&oldid=prevPhilip: /* Summary */2022-08-03T21:25:08Z<p><span dir="auto"><span class="autocomment">Summary</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 21:25, 3 August 2022</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Summary==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Summary==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>There isn't much to go wrong inside digital weighing scales apart from physical problems <del style="font-weight: bold; text-decoration: none;">which </del>should be visible on close inspection. <del style="font-weight: bold; text-decoration: none;">Nevertheless, their </del>principles of operation are interesting, and an understanding will help diagnose any faults which aren't visually obvious.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>There isn't much to go wrong inside digital weighing scales apart from <ins style="font-weight: bold; text-decoration: none;">possibly the LCD and the push buttons, which may be fixable. Other </ins>physical problems should be visible on close inspection. <ins style="font-weight: bold; text-decoration: none;">The </ins>principles of operation are interesting, and an understanding will help <ins style="font-weight: bold; text-decoration: none;">you </ins>diagnose any faults which aren't visually obvious.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Principles of operation==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Principles of operation==</div></td></tr>
</table>Philiphttps://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=2758&oldid=prevPleriche: /* Identifying load cell connections */2019-05-28T08:46:20Z<p><span dir="auto"><span class="autocomment">Identifying load cell connections</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 08:46, 28 May 2019</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l52">Line 52:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Should you need to identify the connections to a load cell (for example if 2 or more are broken) you can do so quite easily with a [[Glossary:Multimeter|multimeter]] on a 2kΩ [[Glossary:Resistance|resistance]] range.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Should you need to identify the connections to a load cell (for example if 2 or more are broken) you can do so quite easily with a [[Glossary:Multimeter|multimeter]] on a 2kΩ [[Glossary:Resistance|resistance]] range.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>For a half-bridge load cell (3 wires only), this contains just 2 strain gauges. Find one wire that measures the same resistance to either of the other two. This is the centre point of the two strain gauges, and the resistance between those other two should read twice as much. Wiring 4 such load cells into a Wheatstone bridge, the 4 centre points are the + and - inputs, and the two outputs. Th other wires are all connected in pairs of the same colour (see the diagram earlier).</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>For a half-bridge load cell (3 wires only), this contains just 2 strain gauges. Find one wire that measures the same resistance to either of the other two. This is the centre point of the two strain gauges, and the resistance between those other two should read twice as much. Wiring 4 such load cells into a <ins style="font-weight: bold; text-decoration: none;">[[Digital_weighing_scales#Wheatstone_Bridge_Connection|</ins>Wheatstone bridge<ins style="font-weight: bold; text-decoration: none;">]]</ins>, the 4 centre points are the + and - inputs, and the two outputs. Th other wires are all connected in pairs of the same colour (see the diagram earlier).</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A full bridge load cell has 4 wires and contains 4 strain gauges in a Wheatstone bridge. Measure the resistance from any one wire to each of the other three in turn. One should measure more than the other two, to be precise, two and two thirds as much. This is the opposite corner of the bridge. It doesn't matter which pair of corners you use as + and - inputs and which as outputs, but if the scales give negative weights, just swap the two wires of one pair.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A full bridge load cell has 4 wires and contains 4 strain gauges in a Wheatstone bridge. Measure the resistance from any one wire to each of the other three in turn. One should measure more than the other two, to be precise, two and two thirds as much. This is the opposite corner of the bridge. It doesn't matter which pair of corners you use as + and - inputs and which as outputs, but if the scales give negative weights, just swap the two wires of one pair.</div></td></tr>
</table>Plerichehttps://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=2757&oldid=prevPleriche: /* Identifying load cell connections */2019-05-28T08:44:32Z<p><span dir="auto"><span class="autocomment">Identifying load cell connections</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 08:44, 28 May 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Identifying load cell connections==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Identifying load cell connections==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Should you need to identify the connections to a load cell (for example if 2 or more are broken) you can do so quite easily with a multimeter on a 2kΩ resistance range.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Should you need to identify the connections to a load cell (for example if 2 or more are broken) you can do so quite easily with a <ins style="font-weight: bold; text-decoration: none;">[[Glossary:Multimeter|</ins>multimeter<ins style="font-weight: bold; text-decoration: none;">]] </ins>on a 2kΩ <ins style="font-weight: bold; text-decoration: none;">[[Glossary:Resistance|</ins>resistance<ins style="font-weight: bold; text-decoration: none;">]] </ins>range.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For a half-bridge load cell (3 wires only), this contains just 2 strain gauges. Find one wire that measures the same resistance to either of the other two. This is the centre point of the two strain gauges, and the resistance between those other two should read twice as much. Wiring 4 such load cells into a Wheatstone bridge, the 4 centre points are the + and - inputs, and the two outputs. Th other wires are all connected in pairs of the same colour (see the diagram earlier).</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For a half-bridge load cell (3 wires only), this contains just 2 strain gauges. Find one wire that measures the same resistance to either of the other two. This is the centre point of the two strain gauges, and the resistance between those other two should read twice as much. Wiring 4 such load cells into a Wheatstone bridge, the 4 centre points are the + and - inputs, and the two outputs. Th other wires are all connected in pairs of the same colour (see the diagram earlier).</div></td></tr>
</table>Plerichehttps://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=2756&oldid=prevPleriche: /* Strain Gauges */2019-05-28T08:39:31Z<p><span dir="auto"><span class="autocomment">Strain Gauges</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 08:39, 28 May 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Domestic weighing scales use strain gauges to measure the tiny deformations of a piece of metal under load.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Domestic weighing scales use strain gauges to measure the tiny deformations of a piece of metal under load.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A strain gauge is extremely simple. A zigzag resistive track on a foil backing is elongated and becomes thinner as it is stretched (within its elastic limit), increasing its resistance. Conversely, if it is compressed (so long as it doesn't buckle), its resistance is reduced.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A strain gauge is extremely simple. A zigzag resistive track on a foil backing is elongated and becomes thinner as it is stretched (within its elastic limit), increasing its <ins style="font-weight: bold; text-decoration: none;">[[Glossary:Resistance|</ins>resistance<ins style="font-weight: bold; text-decoration: none;">]]</ins>. Conversely, if it is compressed (so long as it doesn't buckle), its resistance is reduced.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:StrainGaugeAnim.gif|180px|thumb|right|A Wheatstone bridge consisting of 4 strain gauges produces an output when two of them are stretched and the other two compressed.]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:StrainGaugeAnim.gif|180px|thumb|right|A Wheatstone bridge consisting of 4 strain gauges produces an output when two of them are stretched and the other two compressed.]]</div></td></tr>
</table>Plerichehttps://wiki.restarters.net/index.php?title=Digital_weighing_scales&diff=2259&oldid=prevPleriche: /* Fault-finding and Repair */2019-02-07T17:30:59Z<p><span dir="auto"><span class="autocomment">Fault-finding and Repair</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 17:30, 7 February 2019</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l43">Line 43:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Check there is nothing obstructing the load cell or cells and their wires aren't broken. The wires are often quite thin. The wires should be routed neatly from the load cell or load cells to the circuit board, ideally, lightly twisted together. If excessively long and loosely routed it is possible that nearby mains wiring could induce currents which could cause inaccurate or inconsistent readings.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Check there is nothing obstructing the load cell or cells and their wires aren't broken. The wires are often quite thin. The wires should be routed neatly from the load cell or load cells to the circuit board, ideally, lightly twisted together. If excessively long and loosely routed it is possible that nearby mains wiring could induce currents which could cause inaccurate or inconsistent readings.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Missing rows of pixels on the display can be caused by poor contact between the LCD and the circuit board it's mounted on. Sometimes the connection is made by a strip of conductive rubber which only conducts across its width and not along its length. If you can somehow increase the pressure or clean both the circuit board and the contact area of the LCD you may be able to improve it.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Missing rows of pixels on the display can be caused by poor contact between the LCD and the circuit board it's mounted on. Sometimes the connection is made by a strip of <ins style="font-weight: bold; text-decoration: none;">[[Connectors#Elastomeric_.28or_ZEBRA.29_connectors|</ins>conductive rubber<ins style="font-weight: bold; text-decoration: none;">]] </ins>which only conducts across its width and not along its length. If you can somehow increase the pressure or clean both the circuit board and the contact area of the LCD you may be able to improve it.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Push buttons can become unreliable with use. Often, the button on the control panel is simply a piece of plastic which actuates a [[Passive_components#Switches and Push-Buttons|tactile push button switch]] underneath. These are readily available in a range of fairly standard sizes.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Push buttons can become unreliable with use. Often, the button on the control panel is simply a piece of plastic which actuates a [[Passive_components#Switches and Push-Buttons|tactile push button switch]] underneath. These are readily available in a range of fairly standard sizes.</div></td></tr>
</table>Pleriche