Trying to get a guess at which of my meters are most accurate
since I do not have a reference source to calibrate against.
Significant standard deviation here.  I may have to say my Tek, BK, and Fluke
are pretty darn close together and very close to the average of all my
meters and probably close to the real voltage...<br>
3&frac12;=1999 count<br>
3&frac34;=3999 count<br>
4&frac12;=19999 count<br>
<table border=1>
<tr><th>Meter</th><th>Amplifier or ADC IC</th><th>Method<sup>3</sup></th><th>Display</th><th rowspan=1>12V SLA<br>Werker</th><th rowspan=1>6V SLA<br>PowerSonic</th><th>InputRes</th><th>Cont<br>Beeper<sup>4</sup></th><th>power</th><th>Notes</th></tr>
<tr><th><a href="bkp2833/">BK Precision 2833</a></th><td>ICL7129</td><td>INT</td><td>LCD 4&frac12;</td><td>?</td><td>?</td><td>11M&Omega;</td><td>Latch</td><td>6xUM2 (measured ~ 5mA, est 800h), or 7.5VDC</td><td>"Portable" benchtop, true RMS</td></tr>
<tr><th>Centech HFT#92020 aka <a href="mastech_m830b.gif">Mastech M830B w/lit display</a></th><td>ICL7106 clone die</td><td>INT</td><td>backlit LCD 3&frac12;</td><td>12.92</td><td>6.39</td><td>1M&Omega;</td><td>NA</td><td>PP3 (200h)</td><td>hFE, Backlight</td></tr>
<tr><th>Centech P33499 aka <a href="mastech_m300.gif">Mastech M300</a></th><td>ICL7106 clone die</td><td>INT</td><td>LCD 3&frac12;</td><td>13.00</td><td>6.43</td><td>1M&Omega;</td><td>Fast</td><td>A23 (est. 20h)</td><td>attached probes, pocket</td></tr>
<tr><th>Centech 96308 <sup>1</sup></th><td>ICL7106 clone die?</td><td>INT</td><td>LCD 3&frac12;</td><td>12 ?</td><td>6 ?</td><td>9M&Omega;</td><td>Latch</td><td>3xCR2032, measured 2.33mA, est 90h</td><td>Clamp 20A/200A/400A AC, 300V AC/DC, 2000/200K&Omega;</td></tr>
<tr><th><strike>Centech P98674 aka <a href="ms8229/">Mastech MS8229</a></strike></th><td><strike><a href="ms8229/fs9721_lp3.pdf">FS9721</a> die</strike></td><td>INT</td><td><strike>backlit LCD 3&frac34; (3999)</strike></td><td>12.96</td><td>6.41</td><td>10M&Omega;</td><td>Fast</td><td>3xUM4 (est. 300h, backlight will reduce to ~70h)</td><td><strike>Autorange+Lux/dB/RH/Temp/Backlit, 10A AC/DC,</strike> BROKEN/FAILED</td></tr>
<tr><th><a href="fluke">Fluke 77</a><sup>1</sup></th><td>Custom</td><td>INT</td><td>LCD 3&frac34; (3199)</td><td>?</td><td>?</td><td>11M&Omega;</td><td>Latch</td><td>PP3 9V (rated 1600h for CZn)</td><td>handheld Autorange</td></tr>
<tr><th>HP 3466A<sup>1</sup></th><td>Custom</td><td>INT</td><td>Red LED 4&frac12;</td><td>?</td><td>?</td><td>10M&Omega;</td><td>NA</td><td>120V AC, 3xCyclon 2V 2.5Ah SLA, est. 3 hr</td><td>"Portable" benchtop, True RMS</td></tr>
<tr><th>Dana 4600<sup>1</sup></th><td>Custom/Fairchild 3814</td><td>INT</td><td>Yellow LED 4&frac12;</td><td>?</td><td>?</td><td>10G&Omega;, 10M&Omega;</td><td>NA</td><td>120V AC</td><td>"Portable" benchtop</td></tr>
<tr><th>Tektronix DM502</th><td>LD111 DIP</td><td>INT</td><td>Red LED 3&frac12;</td><td>12.94</td><td>6.40</td><td>1+G&Omega;, 10M&Omega;</td><td>NA</td><td>120V AC</td><td>Module for TM50x cabinet, hacked standalone</td></tr>
<tr><th>Tenma 72-4025</th><td><a href="UMECD001-6-27.pdf">UM7108F</a> QFP</td><td>INT</td><td>LCD 3&frac12;</td><td>12.91</td><td>6.38</td><td>10M&Omega;</td><td>Fast</td><td>PP3 (Alkaline 565mAh/2.6mA drain = about 200h)</td><td>hFE,Hz,10A AC/DC</td></tr>
<tr><th><a href="../wd750a/">Viz WD-750A</a> Voltohmyst</th><td>LD111 DIP</td><td>INT</td><td>Red LED 3&frac12;</td><td>12.88</td><td>6.31</td><td>10M&Omega;</td><td>NA</td><td>120V/240V<br>4xNiCd C (4h?)</td><td>"Portable" LED, metal case</td></tr>
<tr><th>AW Sperry <a href="http://www.sperryinstruments.com/en/resources/legacy">SP-5A (legacy meter)</a><sup>1</sup></th><td>NONE</td><td>MagMv</td><td>Mirrored Scale Analog, AC=Halfwave</td><td>13</td><td>6.2</td><td>2K&Omega;/V</td><td>-</td><td>DUT, UM3 for Rx1K&Omega;</td><td>Pocket Analog</td></tr>
<tr><th><a href="eico555/">Eico Model 555</a><sup>1</sup></th><td>NONE</td><td>MagMv</td><td>Analog, AC=Halfbridge</td><td>?</td><td>?</td><td>20K&Omega;/V</td><td>-</td><td>DUT, 1xUM1 for Rx1&Omega; Rx100&Omega; Rx10K&Omega;, 4xUM3 for Rx10K&Omega;</td><td>Standard Analog multimeter</td></tr>
<tr><th><a href="rs22-216/">Radio Shack 22-216</a><sup>1</sup></th><td>SSI CMOS, NJM062M, LM2902, LM4558</td><td>MagMv</td><td>Mirrored Scale Analog, precision op amp rectifier</td><td>?</td><td>?</td><td>10M&Omega; or 1M&Omega; in mV range</td><td>Fast</td><td>4xUM3 est. 250 hours</td><td>FETVM Autorange</td></tr>
<tr><th><strike><a href="hk-v7a">Heathkit V7A</a><sup>1</sup></strike></th><td><strike>12AU7 Vacuum Tube</strike></td><td>MagMv</td><td>Analog AC=6AL5 halfbridge</td><td>-</td><td>-</td><td>11M&Omega;</td><td>NA</td><td>120VAC, 1xUM2 for &Omega; modes</td><td><strike>VTVM </strike> SOLD</td></tr>
<tr><th><a href="cea/">Craftsman Engine Analyzer</a><sup>1</sup></th><td>NONE/icl7611</td><td>MagMv</td><td>Analog</td><td>?</td><td>?</td><td>625&Omega;/V</td><td>NA</td><td>DUT, 1xPP3 for Rx1/Rx1K&Omega;</td><td>Analog Car engine Analyzer, included because it can measure volts, amps, ohms just like a multimeter...</td></tr>
<tr><th><strike><a href="sim200mv.jpg">Simpson 200mV</a><sup>1,2</sup></strike></th><td><strike>ICL7107 DIP</strike></td><td>INT</td><td>LED 3&frac12;</td><td>-</td><td>-</td><td>1M&Omega;</td><td>No &Omega;</td><td>5VDC</td><td><strike>Panel Meter</strike> SOLD</td></tr>
<tr><th>Breadboard Test</a><sup>1,2</sup></th><td>TC7116CPL DIP</td><td>INT</td><td>LCD 3&frac12;</td><td>-</td><td>-</td><td>1M&Omega;</td><td>No &Omega;</td><td>9VDC</td><td>Breadboard, plan transfer to PCB</td></tr>
<tr><th>Homemade Digital PSU<sup>1,2</sup></th><td>AVR90S4433</td><td>SAR</td><td>LCD HD44780</td><td>about 12.5</td><td>about 6.2</td><td>~50K&Omega;</td><td>No &Omega;</td><td>120VAC</td><td>uncalibratable</td></tr>
<tr><th><a href="benchpsu/">Homemade Analog PSU</a><sup>1,2</sup></th><td>NONE</td><td>MagMv</td><td>Analog</td><td>about 12.6</td><td>about 6.2</td><td>1K&Omega;/V</td><td>No &Omega;</td><td>120VAC</td><td>uncalibratable</td></tr>
</table>
<sup>1</sup> Not used in calibration<br>
<sup>2</sup> Not a multimeter, added for comparison<br>
<sup>3</sup> Integrating, Magnetic Movement, Successive Approximation Register<br>
<sup>4</sup> Continuity Beeper.  Mode where it sounds a buzzer when a low
resistance is connected.  Fast = no lag, Latch = latched/slight lag. NA = this
multimeter requires power during use but does not have continuity beeper. A
hyphen means that this feature is not practical due to power requirements.<br>
<p>
The FS9721 supports RS232-out and was hacked into my P98674.<br>
The UM7108F supports serial-out but requires a microcontroller
to support RS232-out to convert the 16-bit raw data to RS232.  
This may be a project in the future - a RS232 capable microcontroller with
2 input ports (receive data, End of Conversion) and 1 output port (clock) is
needed.  I have plenty of AVR90S2313's that could be used...  A tiny AVR with
software RS232 may work too.<br>
<p>
Average 12V battery: 12.935V<br>
Standard Deviation: 0.0382<br>
<p>
Average 6V battery: 6.387V<br>
Standard Deviation is 0.0377<br>
<p>
I probably shouldn't trust my WD750A and the P33449?
Tried to calibrate the P33449 to the Tektronix,
unfortunately now my average and std deviation changed...<br>
<a href="meters2.html">New Voltage Analysis</br>