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Wiring – Campbell Scientific HMP45C Temperature and RH Probe User Manual

Page 9

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Model HMP45C Temperature and Relative Humidity Probe

4. Wiring

Connections to Campbell Scientific dataloggers are given in Tables 4-1
through 4-3. The probe can be measured by two single-ended or differential
analog input channels.

When measuring the HMP45C with single-ended
measurements, the purple or white and black leads must
both be connected to AG on the CR10(X) and
CR500/CR510 or to

on the CR1000, CR5000, and

CR23X. Doing otherwise will connect the datalogger’s
analog and power ground planes to each other, which in
some cases can cause offsets on low-level analog
measurements. To avoid 4 mA flowing into analog ground,
switch the sensor on/off for its own measurement.

CAUTION

TABLE 4-1. Connections for Single-Ended Measurements




Color




Description




CR10X

CR1000,
CR3000,

CR800,

CR5000,

CR23X


CR10,

CR510,

CR500




21X, CR7

Yellow Temperature

Signal

Single-Ended

Input

Single-Ended

Input

Single-Ended

Input

Single-Ended

Input

Blue Relative

Humidity

Signal

Single-Ended

Input

Single-Ended

Input

Single-Ended

Input

Single-Ended

Input

White Signal

Reference

AG

AG

Black Power

Ground

AG

AG

Shield Shield

G

G

Red Power

Continuous/Switched

SW12V SW12V

12V/SW12V*

12V/SW12V*

CR10X Power Control

if using SW12V

channel on datalogger

Jumper from

SW12V Control to

Control Port

*On these dataloggers switched power is only available with the SW12V peripheral.

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