Experimental Physics and
Industrial Control System

Ying Wu <[email protected]> · Thu, 13 Oct 1994 23:11:12 -0400

Hi,

Recently we fixed a problem with the readback from an Allen Bradley 
IXE used as a millivolt module. What we have seen is that the linear 
conversion for the device type "AB-1771IXE-Millivolt In" is
bypassed in devAllenBradley.c. RVAL is returned as VAL even if linear
conversion is selected in the database. 

Without further information about how to use the RVAL value, 
I used a volt-meter to measured the voltage applied to the AB1771-IXE, 
and then compared the measurement with RVAL. It turns out that 
the voltage reading in millivolt is RVAL divided by 100. 

Note: one cannot distinguish a negative voltage reading from a positive 
      one only using RVAL.

Here is the measurement,

 Raw voltage measured           VAL(or RVAL) from an
 by a volt-meter (mV)           AB1771-IXE used 
				a millivolt module
-----------------------------------------------------------------------------
  8.5                            858
 47.2                           4722
 82.2                           8207
 -8.5                            858
-47.2                           4713
-82.2                           8193
-----------------------------------------------------------------------------

Could someone confirm this observation, or correct me if it is wrong ?

Thanks in advance !

Ying

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System