MEP EP#240: Disturbed Solder Accuracy

<h4><a href="https://macrofab.com/blog/mep-ep240-disturbed-solder-accuracy">MEP EP#240: Disturbed Solder Accuracy</a><br></h4><h4>Parker</h4> <ul> <li>Got a fully automatic screen printer! <ul> <li>ESE US-2000X</li> <li>Potentially lower our minimal paste size</li> </ul> </li> <li>Twitch Live Stream podcasts?</li> <li><a href="https://www.amazon.com/Multimeter-Precision-Gold-Plated-Alligator-Extension/dp/B07TQMDXJH" target="_blank" rel="noopener">Amazon multimeter probes</a></li> </ul> <h4>Stephen</h4> <ul> <li>High voltage low current measurement <ul> <li>Don't want to break the connection so a traditional ammeter isn't going to work</li> <li>Sticking with the read both sides of a resistor method</li> <li><a href="http://www.caddock.com/Online_catalog/Mrktg_Lit/Type1776.pdf" target="_blank" rel="noopener">Caddock 1776-C681</a> high voltage high resistance high tolerance divider <ul> <li>1/100 so 0 to 500v becomes 0 to 5v</li> </ul> </li> <li>ADC - <a href="https://www.mouser.com/ProductDetail/Microchip-Technology/MCP3551-E-SN?qs=usxtMOJb1RxFVP%252BUZib4lg%3D%3D" target="_blank" rel="noopener">MCP3551-E/SN</a> <ul> <li>22 bit</li> <li>SPI</li> <li>2.4 meg ohm input impedance</li> </ul> </li> <li>Ideally the voltage divider has a “gain” of 0.01 but if the ADC is directly attached to the divider the gain is around 0.0096 <ul> <li>Full scale would be 4.8V instead of 5V</li> </ul> </li> <li>Solution: add a buffer</li> <li><a href="https://www.mouser.com/ProductDetail/Analog-Devices/AD8244BRMZ?qs=y2kkmE52mdMBn%252BTWXbBmJg%3D%3D" target="_blank" rel="noopener">AD8244BRMZ</a> <ul> <li>Quad buffer </li> <li>Typical offset voltage of 100uV</li> <li>Gain error of 0.03% max on +/-15v rails </li> <li>10T ohm and 4pf input resistance/capacitance - 10^12</li> <li>Gain error is now 0.009999999901 - Close enough</li> </ul> </li> </ul> </li> </ul>