mar. 22 novembre 2016

HP 3456A Digital Voltmeter

A very long time ago, I bought a venerable HP 3456A Digital Voltmeter. Back then, I had no clear idea what kind of device it is; but it was cheap. It worked quite fine (it is indeed not calibrated), but I noticed for a while that it was quite unstable ...

dim. 18 septembre 2016

HP 34970A Data Acquisition Unit - communication protocol

In order to build a replacement display for the HP34970A data acquisition unit, I needed to understand the communication protocol between the CPU board and the front panel assembly.

General description

The unit is built with four boards:

  • A1 is the main bard, with the PSU, the main controller and ...

sam. 17 septembre 2016

HP 34970A Data Acquisition Unit - part 4

After a summer pause, I'm back on my HP34970A replair project. In the previous post in this series, I've started to reverse ingineer the serial protocol between the CPU board and the fonrt panel, and implement a prototype of replacement display.

OLED display

I bought the bigest OLED ...

dim. 26 juin 2016

HP 34970A Data Acquisition Unit - part 3

As explained in the previous post in this series, I've started to sniff the serial protocol between the main board and the display panel so I can replace the failed VFD by an OLED or TFT display managed by an arduino or similar.

Protocol

The serial communication takes place ...

mer. 22 juin 2016

HP 34970A Data Acquisition Unit - part 2

This is quick follow up of my previous blog post on my attempt to fix my recently acquired HP 34970A.

In my hurry to replace the failing FRAM (FM24C04) chips, I also replaced the FRAM chip on one of my 2 plugin modules.

Bad idea: the module then provoques an ...

lun. 13 juin 2016

HP 34970A Data Acquisition Unit

I recently "scored" a HP 34970A with the DMM included and 2 plugin cards (HP 34901A and HP 34907A) for less than 200€. The plugins should be in working condition, but the main switch unit was almost "given" with the plugin modules since it is non functional.

front view of the HP 34970A data acquisition unit

It's in ...