Good day Ian,
I trust this message finds you well.
Here is my final, working setup for a Keithley 195 (non-A) digital multimeter/DMM for your excellent program. That is one of those "brown boxes" from the early 80s. It has a proprietary command set for remote programming; i.e. the command set is not SCPI-compatible. Successfully tested your program with a NI VISA installation. Screenshot attached.
Here are the settings for your program:
"STB mask" set to "16" (default)
"Enable Polling" disabled
"Remove 1st two letters" disabled
"Abort Errors" enabled
"Terminator" disabled
"Send Blocking" enabled
In the "Pre run" entry field:
F0Z1R1P2S6W0A0G1T4X
In the "At run:" entry field:
No entry
Configuration details for the type 195 device. Reference: Keithley 195 Publication Date: August 1983 Document Number: 195-901-0IC
Section 4.10 DEVICE-DEPENDENT COMMAND PROGRAMMING
"F0Z1R1P2S6W0A0G1T4X" configures the Keithley type 195 DMM as follows:
F0 = DC Volts
Z1 = Zero-ing
R1 = Range 20 mV
P2 = Filter off, 32 samples averaged for 5 1/2 digits
S6 = 100 ms integration period, 5 1/2 digits
W0 = min. delay.
A0 = Enable internal multiplex routines (for accuracy)
G1 = Readings without prefix/suffix.
T4 = Trigger Continuous on X commands
X = Execute
I am also including a histogram and a trend plot taken with MS Excel based on 3,500 readings at 5 sec each.
Excel's internal formulas calculated a few parameters as follows:
AVERAGE of -1.58µV
AVEDEV as average of the absolute deviations from mean is 0.161 µV
and a STDEV.P standard deviation of 0.203µV.
If I follow the "six sigma"-theory, then 6 x sigma equals 1.22 µV, which I believe is not too shabby for a 5 1/2 digit multimeter with a basic 24-hour accuracy of 100 ppm plus 40 counts for the 20mV DC range.
The last calibration was in July 2014.
I am not a "volt nut". I was simply curious about the unit's performance. I have shortened the inputs with a bare, short 0.5 mm² / AWG 20 copper wire.
The unit was exposed to some regular temp. difference over the day, i.e. between approx 18 and 24 degrees C in my room.
Cheers,
THDplusN_bad