Michael, Just a side note here on adjusting the 3 calibration pots inside the front panel of the 732A
Fluke did supply an adjustment tool with each 732A but I don't know exactly who made it or what model number. I use a General Cement ( GC ) model 8276 adjustment tool, the end with the blade recessed, to do the job. Sometimes it takes a little fiddling and patience to get the adjustment tool to engage the slot in the pot, but it can be done and without any danger of shorting something out. http://www.alliedelec.com/search/productdetail.aspx?SKU=70159521 360 uvolts ( 36 ppm ) above 10 volts seems more than a little high for one of these units. The worst I have seen over 6 units is around 120 uvolts ( 12 ppm ) out of spec, but I was able to bring it in by changing the jumpers on the A7 board. It is conceivable that someone totally screwed up the last calibration. You would need to take off the top cover, the top guard cover, remove the top foam piece and take a look at the jumpers on the A7 board. The one thing I can't remember right now is if shorting the resistors R12 through R17 on the A5 board, by adding or removing jumpers on the A7 board lowers or raises the output voltage at 10 volts. But in the manual I did find an addendum to paragraph 4-38 which says. "Cutting a jumper increases the 732A 10 V output the amount labeled above the jumper. Likewise, completing a jumper decreases the output the amount of the jumper label". So that should help you once you view the jumpers on the A7 board. I do know that you can add or remove multiple jumpers on the A7 board so the total range of the change in the 10 V output can be around 750 uvolts ( 75 ppm ). If you see many jumpers on the A7 board this would mean that someone tried to lower the output voltage and that the reference could not be adjusted properly to exactly 10 V. In other words if you see no jumpers on the A7 board then you could possibly bring the output to exactly 10 V from it's present ( presumed ) 36 ppm too high. You really need a "standard" 10 volts before you do this. But since the seller's DVM is reading 40 ppm too high and your 3457A is reading 36 ppm too high then the output of the 732A is probably also high. What part of the country are you located in? Maybe one of the many "Volt Nuts" lives close to you can give you an idea of what 10 Volts really is. Also I have seen batteries that are so old and messed up that the "Charging" light will never come on. The internal resistance is so high that the charging circuit simply doesn't work. Your thermistor value and stability seems very good so it looks like the oven temperature control circuits are working correctly. I hope the above helps you in determining if you keep the unit or send it back. Bill ----- Original Message ----- From: "J. L. Trantham" <[email protected]> To: "'Michael Hong'" <[email protected]>; "'Discussion of precise voltage measurement'" <[email protected]> Sent: Friday, March 07, 2014 5:57 PM Subject: Re: [volt-nuts] A Fluke 732A: Return it or keep it? Michael, The schematic of the A5 Reference PCB Assembly shows the calibration adjustments and the drawing of that assembly shows the location of the adjustments. They are deep inside the unit. You'll need a small flat bladed tool, a flashlight, and probably a magnifier. I used a length of 12 ga. copper wire with one end flattened to make a screwdriver. Good luck. Joe -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Michael Hong Sent: Friday, March 07, 2014 6:19 PM To: [email protected] Subject: [volt-nuts] A Fluke 732A: Return it or keep it? (3) Front panel calibration hole I put a thin flat blade driver into the holes. I couldn't feel anything until 4 1/4" inside where I felt something but not the potentiometer. volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
