Detecting Open Transducers - HP E1313A Manual

Detecting Open Transducers

Notes
Chapter 4
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Most of the HP E1313/E1413's SCPs provide a method to detect open
transducers. When Open Transducer Detect (OTD) is enabled, the SCP
injects a small current into the HIGH and LOW input of each channel. The
polarity of the current pulls the HIGH inputs toward +17 volts and the LOW
inputs towards -17 volts. If a transducer is open, measuring that channel
will return an over-voltage reading. OTD is available on a per SCP basis.
All eight channels of an SCP are enabled or disabled together. See
Figure 4-9 for a simplified schematic diagram of the OTD circuit.
1. When OTD is enabled, the inputs have up to 0.2µA injected into
them. If this current will adversely affect your measurement, but you
still want to check for open transducers, you can enable OTD, make a
single scan, check the CVT for bad measurements, then disable OTD
and make your regular measurement scans. The specifications apply
only when OTD is off.
2. When Filtering is enabled, allow 15 seconds for the filter capacitors
to charge before checking for open transducers.
Signal Conditioning Plug-on
Signal Input
High
Low
Figure 4-9. Simplified Open Transducer Detect Circuit
+17V
100M
3K
Gnd.
3K
100M
-17V
Understanding the HP E1313/E1413
Multiplexer
High
Low
141