Krohn Hite 523 calibrator Alignment / Adjustment procedure - Page 1
Forum section: electronics / repair

author: Krampmeier
author_rank: Regular Contributor
timestamp: August 05, 2019, 11:04:02 pm
content: At work we have an old Krohn Hite 523 7.5 digit calibratorwhich fails the calibration. It has been in spec for many years without any adjustment, and has now failed. Looks like sending in the unit for factory alignment is not economical in this particular case. I did not have the chance to check the cal history yet, but I will do that in a month in order to see if there was a slow drift or a sudden jump.Unfortunately, the manufacturer does not provide instructions on how to align the thing. Even the normal calibration (verification) routine is secret, you have to buy use the closed-source exe program, which was a PITA to get running..., Krohn Hite?Has anyone found out how the Krohn Hite 523 can be re-adjusted? Are there special GPIB commands for calculating and storing the offset and gain values? I have not opened the unit yet, but I don't assume that it has any variable resistors for that purpose...Any input on this unit, especially related to service and repair, would be interesting...For example, one trap we found is that using the "sense" terminals seems to reduce the accuracy of the output voltage.Thanks in advance for any hints!

author: little.tesla
author_rank: Regular Contributor
timestamp: May 14, 2024, 07:55:45 pm
content: Sorry for resurrecting this thread..I'm as well interested in any information related to the Krohn Hite 523 calibrator. Maybe in the meantime somebody was lucky to gather some additional information.On the web there is only a datasheet and basic user manual available, without any other details e.g. adjustment (apart referring to the commercial calibration software)

author: Krampmeier
author_rank: Regular Contributor
timestamp: May 16, 2024, 10:38:10 pm
content: Some images for those still interested...I don't have any updates regarding alignment of this device yet though.

author: aronake
author_rank: Frequent Contributor
timestamp: July 02, 2024, 10:03:41 am
content: Anyone tired to calibrate a Krohn Hite 523?There is the KH523CAL software mentioned in the manual. But that seems to be 400 USD if bought as an option when buying a new machine.They also mention this in the manual:3.3.3 Full Calibration Command (523 *CAL or 523*cal) This command will place the 523 into its full calibration mode. This cal is not a self-cal and requires external equipment to complete. See calibration instructions for full details.But nowhere is there information in the manual on how the actual calibration is done.My guess is that the machine would output different voltages/current and these voltages/current are keyed in. Thats a pretty common way to calibrate current and voltage sources.

author: little.tesla
author_rank: Regular Contributor
timestamp: July 02, 2024, 06:53:00 pm
content: Recently I've acquired as well one of this calibrators. So far I'm as well still researching regarding the calibration routine/procedure. I've managed to find a copy of the KH523CAL manual and the software on the web. Up to now I have no evidence that the calibrator on its own is able to perform the calibration/adjustment. Analyzing the embedded software would help here.The KH523CAL software is able to perform the calibration, but requires a HP 3458A or FLUKE 8508A for the calibration (hard coded). The calibration software (VB6) checks if the software was bought and activated on the calibrator (option flag). I haven't further examined the software.The unit I have is a more recent model (>2021) with its last cal in 2023. The "bad" thing about this more recent unit is that they updated/changed the CPU which lives on the frontpanel. This new version uses a Parallax SX28AC. Unfortunately I don't have tools to work with this CPU or to examine the embedded software.Data was uploaded to xDevs repo.