Campbell Scientific SDM-INT8 8-Channel Interval Timer - Manual (Page 10)

SDM-INT8 8 Channel Interval Timer
Minimum AC Max Freq.
voltage RMS (Hz)
20 mV 100
50 mV 400
150 mV 1000
2.5 V - 20 V 4000
3. Connections
The CABLE5CBL-L cable connects the SDM-INT8 to a datalogger. The
datalogger-to-SDM-INT8 connections are shown in Figure 3. Please note that
the SDM-INT8 connects to the CR9032 CPU module of the CR9000X and the
CR9080 PAM module of the CR9000. INT8s are shipped from the factory
with a 10K Ohm resistor attached to the terminal strip for the convenience of
21X user. This resistor is necessary only when the INT8 is used with a 21X
datalogger.
Except for the 21X, the order in which the datalogger and
SDM-INT8 connections are made is critical. The
datalogger cases and wiring panel bracket are at
datalogger ground. To avoid accidentally shorting 12 V to
the case, connect the 12 V first then the ground. To
prevent voltages in excess of 5 V from entering the
datalogger’s SDM ports (C1 to C3 or SDM-C1 to SDM-C3),
the ports are wired after connecting the ground lead. CAUTION
For the 21X, a 10K resistor is wired between Control Port 1 and single ended
input 1 (1H). The order in which 21X/INT8 connections are made is not
critical.
The CABLE5CBL-L has a user-specified length. A 1-ft length should be
sufficient when both datalogger and SDM-INT8 are housed in an ENC12/14
enclosure; a 2-ft length may be required if the datalogger and SDM-INT8 are
housed at opposite ends of an ENC16/18. The total cable length for all SDMs
should be as short as possible and preferably does not exceed 20 feet. Longer
lead lengths may be possible for CRBasic dataloggers if the SDMSpeed
instruction is used (see Section 5.1.2). Long lead lengths may prevent
communication.
The signal input lines of the INT8 are protected against the
continuous connection of voltages up to 20 VDC and
against high voltage electrostatic discharge. However,
where there are long cable runs (>3 m) to the sensor and
particularly when the cables run outside, some extra
protection may be required for these inputs to protect the
inputs against high energy surges, as may be induced by
lightning. Please contact Campbell Scientific for further
advice. CAUTION
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