Measurement Computing USB-5203 - Manual (Page 11)

USB-5203 User's Guide Sensor Connections
11
Do not connect two different sensor categories to the same channel pair
The USB-5203 provides a 24 bit A/D converter for each channel pair. Each channel pair can monitor one sensor
category. To monitor a sensor from a different category, connect the sensor to a different channel pair (input
terminals).
Current excitation output terminals (±I1 to ±I4)
The USB-5203 has four dedicated pairs of current excitation output terminals (± I1 to ± I4 ). These terminals have
a built-in precision current source to provide excitation for the resistive sensors used for RTD and thermistor
measurements.
Each current excitation terminal is dedicated to one pair of sensor input channels:
 I1+ is the current excitation source for channel 0 and channel 1
 I2+ is the current excitation source for channel 2 and channel 3
 I3+ is the current excitation source for channel 4 and channel 5
 I4+ is the current excitation source for channel 6 and channel 7
Four-wire, two sensor common terminals (4W01 to 4W67)
These terminals are used as the common connection for four-wire configurations with two RTD or thermistor
sensors.
Two sensor common terminals (IC01 to IC67)
These terminals are used as the common connection for two-wire configurations with two RTD or thermistor
sensors.
Digital terminals (DIO0 to DIO7)
You can connect up to eight digital I/O lines to the screw terminals labeled DIO0 to DIO7 . Each terminal is
software-configurable for input or output.
If a digital bit is set up as an alarm, the bit is configured for output on power-up, and assumes the state defined
by the alarm configuration.
CJC sensors
The USB-5203 has two built in high-resolution temperature sensors. One sensor is located on the right side of
the package, and one sensor is located on the left side.
Power terminals (+5V)
The two +5V output terminals are isolated (500 VDC) from the USB +5V.
Caution! Each +5V terminal is an output. Do not connect to an external power supply to these terminals or
you may damage the USB-5203 and possibly the computer.
Ground terminals (GND)
The six ground terminals ( GND ) provide a common ground for the input channels and DIO bits and are isolated
(500 VDC) from the USB GND.
Thermocouple connections
The USB-5203 makes fully-differential thermocouple measurements without the need of ground-referencing
resistors. A 32-bit floating point value in either a voltage or temperature format is returned by software. An
open thermocouple detection feature is available for each analog input which automatically detects an open or
broken thermocouple.
Use InstaCal to select the thermocouple type (J, K, R, S, T, N, E, and B) and one or more sensor input channels
to connect the thermocouple.