I spent some of today attempting to calibrate a 7081 that has had the EAROM chip (ER3400) on the in-guard (floating) logic board replaced. For each calibrate command issued I get a "Cal Incomplete" message rather than a "Cal OK" message (this *may* be OK, or *may* be a fault). When I try to issue calibrate, reference, 10.00000 I get a message "Factor out of range" (all other VDC, VAC, and KOHM calibrate commands worked apart from the Cal Incomplete message). Does anyone know what the problem is, or have any thoughts as to what the probable cause might be? On a very related point, how do you calibrate the Ratio calibration constant (there's nothing in either the Service manual or the Test Specification about this other than item 21 in the automated checks section on page 16 which says: 22. Ratio - ratio is calibrated. Dave

After a great deal of messing around and experimentation, I have resolved the problem. On the other 7081 I have, the meter accepted the calibrate reference command with the "reference supply of approximately 10 volts DC" connected to the front panel input. On this meter this reference supply needed to be applied to the "ratio reference" input DIN socket on the REAR panel. Once this was done all was well. I completely fail to comprehend how this command actually worked on the other meter, as it is now clear that "calibrate reference" is actually doing the RATIO calibration. So on page 8.11 of your maintenance manual you should amend the bullet point near the top of the page which reads: * Connect a reference of approximately 10 volts dc to the input. so that it reads: * Connect a reference of approximately 10 volts dc to the ratio reference input on the rear of the meter. Dave -----Original Message----- From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of David C. Partridge Sent: 21 April 2016 20:53 To: 'Discussion of precise voltage measurement'; Solartron_Schlumberger_Equipment@groups.io Subject: [volt-nuts] Solartron 7081 calibration problems > When I try to issue calibrate, reference, 10.00000 I get a message "Factor out of range" (all other VDC, VAC, and KOHM calibrate commands worked apart from the Cal Incomplete message).