GPIB board for calibrating AM503B, or alternatives?


Jared Cabot
 

I have a bunch of AM503B modules here, all with dead and leaking batteries that I am in the process of replacing.

It seems that according to the service manual, the only way to set calibration constants in these units is with a GPIB board that is installed during the calibration process.

Does anyone happen to have a GPIB board to suit the AM503B, or one pulled from an AM5030 that they are willing to sell, or is there any known workaround to do the calibration a different way?


Rico Sonderegger
 

Hi Jared,

I have 3 of these GPIB adapters (have 3 x AM5030B).
I wanted to program the serial number and it didn't work. So I connected a logic analyzer to see what was going on.
If you only want to update the calibration data, you can program the addresses 0xE0-00xE1 (CALC 00 or RinX1 value), 0x0B-0X0C (CALC 01 or RinX10 value) and 0xCA-0xCB (CALC 02 or RinX100 value) in the PCF8570 (Base address= 0xA0) on the I2C bus with "Bus Pirate".
The calibration data are stored there. After changing the battery, 0x61A8 (= 25000) remains there.

Best regards
Rico


Jared Cabot
 

Oh, cool. Thanks for that. I guess I'll have to get onto learning how to use a Bus Pirate now, unless you want to sell one of your 5030B's (or swap for a 503B :D haha )

Can you provide any more specific info to help me out? I'm not much of a firmware guy.... Even just where to hook the Bus Pirate up and a basic idea how to send commands would be greatly appreciated.


Thanks for the info!


 

Hi Rico,
Since Tek did not provide any support information in the manual for the AM503B I was hoping you found out even more about the internals than this little bit of information.
I am also very interested in knowing exactly how you did this so I can replicate the procedure.
Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Rico Sonderegger
Sent: Sunday, May 09, 2021 6:47 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] GPIB board for calibrating AM503B, or alternatives?

Hi Jared,

I have 3 of these GPIB adapters (have 3 x AM5030B).
I wanted to program the serial number and it didn't work. So I connected a logic analyzer to see what was going on.
If you only want to update the calibration data, you can use the addresses 0xE0-00xE1 (CALC 00 or RinX1 value), 0x0B-0X0C (CALC 01 or RinX10 value) and 0xCA-0xCB (CALC 02 or RinX100 value) on the I2C bus to program the new values in the PCF8570 (base address 0XA0) using a "Bus Pirate".
The calibration data are stored there. After changing the battery, there is 0x61A8 (= 25000).

Best regards
Rico







--
Dennis Tillman W7pF
TekScopes Moderator


Rico Sonderegger
 

Hello Jared,

The "Bus Pirate V4" is connected to the PCF8570 via the signal lines MOSI and CLK.
These "clips" of the logic analyzer can be used for this purpose.
I can not provide any information about the commands at the moment, as my "Bus Pirate" is still on the way from China to me in Switzerland.
As soon as the device arrives, I will send you the necessary commands.

But now to another question.
Do you know why the command to set the serial number in AM5030 = "SERIAL [space] [space] B12345" does not work?
That with the calibration data "CALC 00,25000" works.
That's why I started to measure the data stream with the logic analyzer in order to change this serial number.

Best regards
Rico


Rico Sonderegger
 

Hello Dennis,

With the AM503B, without a GPIB interface, no write processes (except for everything that concerns the operation of the device) can be triggered on the SRAM (PCF8570).
I started by recording the data when "booting" the device and then looking for the value "25000".
This is the "default" value for the calibration data. This is how I found the addresses for these values.
The serial number is in a different area of the SRAM.
In addition, each time a button is pressed on the front panel, this information is saved in the SRAM.
After a "power-up" this information is read back again.

If you want, I can add some screenshots of the data transfer and the connection with the logic analyzer to the "PHOTOS" folder.

Best regards
Rico


 

Hi Rico,
I think screen shots would be great. A picture is worth 1K words.
Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Rico Sonderegger
Sent: Monday, May 10, 2021 4:01 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] GPIB board for calibrating AM503B, or alternatives?

Hello Dennis,

With the AM503B, without a GPIB interface, no write processes (except for everything that concerns the operation of the device) can be triggered on the SRAM (PCF8570).
I started by recording the data when "booting" the device and then looking for the value "25000".
This is the "default" value for the calibration data. This is how I found the addresses for these values.
The serial number is in a different area of the SRAM.
In addition, each time a button is pressed on the front panel, this information is saved in the SRAM.
After a "power-up" this information is read back again.

If you want, I can add some screenshots of the data transfer and the connection with the logic analyzer to the "PHOTOS" folder.

Best regards
Rico







--
Dennis Tillman W7pF
TekScopes Moderator


Jared Cabot
 

I just picked up a Bus Pirate and clips etc today, so I'll start working on figuring out how to use it.

Hopefully with a few minds at it, we can work it out. It would be great if we can figure out a working procedure for future refererence and calibration.


Rico Sonderegger
 

Hello Jared,

I uploaded a draft version of the "HOW-TO" calibrate a AM503B without GPIB.

https://groups.io/g/TekScopes/files/AM503B%20Calibration%20without%20GPIB/AM503B%20Calibration%20without%20GPIB.pdf

Please take a look and give me your changes or suggestions.

Best regards
Rico