Data Translation DT9871, User Manual

Page: 98 / 134

Chapter 6
98
Data Format for Thermocouple Channels
If you specify a thermocouple type of None for a thermocouple input channel, a voltage
measurement is selected and the instrument returns a voltage value. For the DT9871U and
DT9874 instruments, the value is in the range of ±0.075 V; for the DT9872 instrument, the
value is in the range of ±1.25 V. For all other thermocouple types, a temperature value, in
degrees C, or one of the error constants, described on
page 99 , is returned.
In normal operation, one floating-point value is returned for each enabled channel (including
the digital input port). If you enable the capability of returning CJC data in the data stream,
described on
page 91 , two floating-point values are returned in the data stream for each
enabled analog input channel. The first value in the pair represents the temperature (or
voltage) of the channel; the second value in the pair represents the CJC temperature (in
degrees C) for that channel.
Data Format for RTD Channels
If you specify an RTD type of None for an RTD input channel, a voltage measurement is
selected and the instrument returns a voltage value in the range of ±1.25 V. If you specify an
RTD type of Ohms, a resistance value is returned. For all other RTD types, a temperature
value, in degrees C, or one of the error constants, described on
page 99 , is returned.
One floating-point value is returned for each enabled channel (including the digital input
port).
Data Format for Voltage Channels
For voltage channels on a MEASURpoint instrument, a voltage value in the range of ±10 V or
±60 V is returned for each channel, depending on how the channel was configured. Note that
the maximum input voltage for the ±60 V range cannot be more than 30 Vrms, 42.4 Vpk,
60 VDC.
One floating-point value is returned for each enabled channel (including the digital input
port).
Error Conditions
TEMPpoint, VOLTpoint, and MEASURpoint instruments report overrun errors by sending an
overrun event to the application program. If this error condition occurs, the instrument stops
acquiring and transferring data to the host computer. To avoid this error, try one or more of
the following:
• Reduce the sample rate
• Close any other applications that are running
• Run the program on a faster computer