Specifications
4-1
Section 4. Sensor Support
Several features give the CR1000 the flexibility to measure many sensor types.
Contact a Campbell Scientific applications engineer if assistance is required to
assess sensor compatibility.
4.1 Powering Sensors
Read more! See Section 6 Power Supply.
The CR1000 is a convenient source of power for sensors and peripherals
requiring a 5 or 12 VDC source. It has two continuous 12 V terminals (12V),
one program-controlled switched 12 V terminal (SW-12), and one continuous
5 V terminal (5V). SW-12, 12 V, and 5V terminals limit current internally for
protection against accidental short circuits. Voltage on the 12V and SW-12
terminals will change with the DC supply used to power the CR1000. The 5V
terminal is internally regulated to within ±4%, which is typically not adequate
accuracy for bridge sensor excitation. Measurement of the 5 V terminal
voltage output by the datalogger (by means of jumpering to an analog input)
enables an accurate bridge measurement if the 5 V terminal must be used for
excitation. TABLE 4.1-1 shows the current limits of the 12V and 5V
termin
als. Greatly reduced output voltages associated with 12V, SW-12, and
5V due to current limiting may occur if the current limits given in TABLE
4.
1-1 are exceeded.
4.1.1 Switched Precision (-2500 to +2500 mV)
Three switched analog output (excitation) terminals (Vx/EX1, Vx/EX2,
Vx/EX3) operate under program control. Check the accuracy specification of
these channels in Section 3.3 to understand their limitations. Specifications are
only applicable for loads not exceeding ±25 mA. CRBASIC instructions that
control excitation channels include:
BrFull()
BrFull6W()
BrHalf()
BrHalf3W()
BrHalf4W()
ExciteV()
Excitation channels can be configured through the RevEx
parameter of bridge instructions to provide a squarewave AC
excitation for use with polarizing bridge sensors.
4.1.2 Continuous Regulated (5 Volt)
The 5 V terminal is regulated and remains near 5 Volts (±4%) so long as the
CR1000 supply voltage remains above 9.6 Volts. The 5 V terminal is not
suitable for resistive bridge sensor excitation.
NOTE