VXi VT1529A/B 사용자 설명서
Programming the VT1422A for Data Acquisition and Control 155
Changing Gains or
Filters
To change a channel’s SCP setup after a CAL:TARE operation, a *CAL?
operation must be performed to generate new DAC constants and reset the
"range floor" for the stored tare value. The tare capability of the range/gain
setup that the channel is being changed to must also be considered. For
instance, if the actual offset present is 0.6 volts and was "tared" for a 4 volt
range/Gain x1 setup, moving to a 1 volt range/Gain x1 setup will return
Overload values for that channel since the 1 volt range is below the range
floor as set by CAL:TARE. See Table 7-1 on page 294 for more on values
returned for Overload readings.
operation must be performed to generate new DAC constants and reset the
"range floor" for the stored tare value. The tare capability of the range/gain
setup that the channel is being changed to must also be considered. For
instance, if the actual offset present is 0.6 volts and was "tared" for a 4 volt
range/Gain x1 setup, moving to a 1 volt range/Gain x1 setup will return
Overload values for that channel since the 1 volt range is below the range
floor as set by CAL:TARE. See Table 7-1 on page 294 for more on values
returned for Overload readings.
Unexpected Channel
Offsets or Overloads
This can occur when the VT1422A’s Flash Memory contains CAL:TARE
offset constants that are no longer appropriate for its current application.
Execute CAL:TARE:RESET then *CAL? to reset the tare constants in RAM.
Measure the affected channels again. If the problems go away, then the tare
constants in Flash memory by executing CAL:STORE TARE can be reset.
offset constants that are no longer appropriate for its current application.
Execute CAL:TARE:RESET then *CAL? to reset the tare constants in RAM.
Measure the affected channels again. If the problems go away, then the tare
constants in Flash memory by executing CAL:STORE TARE can be reset.
Detecting Open Transducers
Most of the VT1422A’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 4-11 for a simplified schematic diagram of the OTD circuit.
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 4-11 for a simplified schematic diagram of the OTD circuit.
S igna l C o nd itio ning P lu g-on
M ultiplexer
S ignal Input
H igh
Low
100M
-17V
3K
G nd.
3K
100M
+17V
H igh
Low
Figure 4-11. Simplified Open Transducer Detect Circuit