Specifications

Detecting Open Transducers
Most of the VT1419A’s analog input 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 3-13 for a simplified schematic diagram of
the OTD circuit.
NOTES 1) When OTD is enabled, the inputs have up to 0.2 µA injected into them. If this
current will adversely affect the measurement, but checking for open transducers is still
required, enable OTD, run the algorithms, check analog input variables for
measurement values that indicate an open transducer, then disable OTD and run the
algorithms without it. The VT1419A’s accuracy specifications apply only when OTD is
off.
Programming the VT1419A Multifunction
Plus
Detecting Open Transducers
100 Chapter 3
Signal Conditioning Plug-On
Signal Input
High
Multiplexer
High
Low
Low
+17 V
-17 V
100 MW
100 MW
3kW
3kW
Gnd
Figure 3-13: Simplified Open Transducer Circuit
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com