It seems like a nice DMM but its pretty old. Judging from the date codes its build somewhere in 1987 / 1988. I'd backup the EPROM just to make sure.
I highly recommend while you have it apart (still?) that you check and re solder the transformer pads.
I worked with equipment that was built in the 1970's ( at latest) which used 2708 eproms. Never had a fault on those boards where the 14 eproms were other than the capacitors going open circuit. They worked even with no capacitors, they were just replaced and found to be open during a blanket change of that particular capacitor as most had failed after 30 years of toasting. No covers either on the chips, enclosed in a hermetic enclosure.AFAIK Eproms are specified to retain their data for 10 to 20 years. You can be lucky but every now and then you see requests from people who would like a copy of the contents of an eprom because their equipment stopped working.
Nice pictures. I have 196 too ( and a 199 and 2000) the 199 is a very good meter. I have one that was given to me by a friend who had three. All three giving the same readings and even now, a few years later it is still spot on.
The 196 was fresh calibrated when I bought it.
But if i read all the horrorstorys about eproms i am afrraid i have to find a way to read and write those. But everytime I ask somebody the answer is, there are o many eproms, which one ? So is it true you need a whole bunch of programmers ? I have one, an old one from the 80's, the DOS software is still available but it uses rs232. I have a toshiba T1000,but that has a problem, gound a box of 720K diskettes and a 3,5 diskdrive to build in my computer but now I have to get that all to work. And if I read this sort of storys I think I must hurry. I have 2 x 7,5 digit and 1x 6,5 digit and a 5,5 digit that ould be in the dangerzone. ( and i'm a severe case of digifobia)
I have one of these Keithley 196 meters, from Ebay, which I have been using for recording the voltage of a LTZ1000 voltage reference. Of course, based on the specs the LTZ1k would be more stable than the meter. Anyway, I am logging data via GPIB and plotting the results. I see, for example, 7.23114 V with daily variations of about +/- 5 counts but every so often (maybe 1x or 2x per day) I get a single reading which is maybe 50 counts off the long term average, then it returns to the baseline. Wonder if its just my meter? Maybe effect of cosmic ray or alpha particle passing through either the meters voltage reference, or the external Vref under test ? I have also tested some other LM399 references and see the same effect.
Apart from certain MOSTEK EEPROMs (used in some HP and Tek products like the HP 3456A) that had manufacturing defects, EEPROMs generally seem to last a very long time. I'm sure there is a small chance for them to fail, but it's not like EEPROMs in instruments from the late eighties are failing in droves.
# Python 2.7 code to get readings from Keithley 196 multimeter via GPIB
# Assumes meter is already set up to correct mode, eg. from front panel
# Dec. 17 2012 J.Beale
from __future__ import print_function # to use print without newline
from serial import *
import time,datetime
cmd = "?\r" # GPIB command to Keithley 196 must end with carriage return
eol_str = "\n" # end of line string in file output
buffer ='' # serial input buffer
outbuf = '' # file output buffer
ser=Serial(17,460800,8,'N',1,timeout=1) # GPIB-USB board on COM18, with 460800 bps, 8-N-1
f = open('K196-log.csv', 'w')
print ("Keithley 196 log v0.1 Dec.17 2012 JPB")
f.write ("date_time,volts\n")
f.write ("# Keithley 196 log v0.1 Dec.17 2012 JPB\n")
while True:
ser.read(255) # clear out existing buffer & throw it away
ser.write(cmd) # send query to instrument
buf = ser.readline() # string terminated with '\n'
buffer = buf.split()[0] # get rid of the \r\n characters at the end
outbuf = str(datetime.datetime.now()) + ',' + buffer
print (outbuf)
f.write (outbuf)
f.write (eol_str)
time.sleep(9) # from 'time' to wait this many seconds
f.close # close log file
ser.close() # close serial port when done. If we ever are...
date_time,volts
# Keithley 196 log v0.1 Dec.17 2012 JPB
2012-12-17 13:25:18.006000,+10.00400E+0
2012-12-17 13:25:28.115000,+10.00401E+0
2012-12-17 13:25:38.147000,+10.00400E+0
2012-12-17 13:25:48.225000,+10.00400E+0
2012-12-17 13:25:58.256000,+10.00400E+0
2012-12-17 13:26:08.365000,+10.00401E+0
2012-12-17 13:26:18.396000,+10.00400E+0