User manual

User Manual
9
8. Wiring
Connections to Campbell Scientific dataloggers for measuring humidity and
temperature using two single-ended or two differential analogue inputs are given
in Tables 8-1 and 8-3. Use a single-ended analogue measurement when the
cable length is less than 6.1 m (20 ft), or if power is switched off between
measurements. For cable lengths longer than 6.1 m or when the probe is
continuously powered, use a differential analogue measurement. See Section 10
for a discussion on errors caused by long cable lengths.
The HC2S3 draws approximately 2 mA powered from 12V. The HC2S3 can be
continuously powered from the 12V terminal, or power can be switched with the
SW12V terminal to conserve battery life. When power is switched, a 3-second
warm-up time is required. Using the SW12V terminal on the CR10X datalogger
requires a user-supplied jumper wire connected between the SW 12V CTRL
terminal and a Control Port (C1..C8).
When measuring the HC2S3 with single-ended
measurements, the yellow and grey 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 analogue and power ground
planes to each other, which in some cases can cause
offsets on low-level analogue measurements. To avoid
2 mA flowing into analogue ground, switch power on/off for
its measurement.
Table 8-1. Connections for Single-Ended Measurements
Colour
Description
CR1000,
CR3000,
CR800,
CR5000,
CR23X
CR10X,
CR10,
CR510,
CR500
Brown Temperature
Signal
Single-Ended
Input
Single-Ended
Input
White Relative Humidity
Signal
Single-Ended
Input
Single-Ended
Input
Yellow Signal Reference
AG
Grey Power Ground
AG
Clear Shield
G
Green Power 12V/*SW12V 12V/*SW12V
*CR10X Power Control if
using SW 12V
Jumper from
SW 12V
CTRL to
Control Port
CAUTION