DEC AXV11-C analog board

[Douglas Taylor]

On 2/8/2022 7:36 PM, Jon Elson via cctalk wrote:
> On 2/8/22 16:35, Douglas Taylor via cctalk wrote:
>> On 2/8/2022 5:22 PM, Jon Elson via cctalk wrote:
>>> On 2/8/22 13:34, Douglas Taylor via cctalk wrote:
>>>> Update on this:  I did put together a battery and voltage divider 
>>>> to test the AXV11.  The label on the A/D module says it brings the 
>>>> output from the multiplexer to one of the external pins.  I was 
>>>> able to verify that the voltage applied to a couple of the A/D 
>>>> inputs makes it through the multiplexer when selected using the 
>>>> CSR.  The next output available is from the Sample and Hold, and 
>>>> this is always pegged at +12v.  Am I wrong to assume that the 
>>>> sample and hold will 'freeze' its output when the A/D go bit is set?
>>>
>>> Well, it will probably only hold the approximate voltage for a few 
>>> seconds, but should be long enough to see on a voltmeter.
>>>
>>> Jon
>>>
>> I was only using a voltmeter to look at it.
>>
>> I'm going to try 2 different measurements; (1) use a scope to look at 
>> the S&H signal on the AXV11 and see what it does over time, (2) look 
>> at the same S&H signal on the Data Translation board which seems to 
>> be working.
>>
> The S&H will likely have a FET as the switch element, and those might 
> be fairly easily damaged by external pulses.  I opened up some 
> comparable Xincom modules and made minor repairs.
>
> Jon
>
Stopped fooling with the AXV11 for now.  Applied various voltages to the 
Data Translation input and recorded the A/D octal values to get an idea 
of what the calibration of the board is.  It looks very linear, +/-10v 
range.

Using a single battery and voltage divider I was able to generate 
voltages on the input of the DT2762 board, however, I had to swap wires 
to get negative voltages.  Is it possible to construct a battery driven 
circuit that will present both positive and negative voltages at the 
input?  A bridge of some sort?

Doug