Campbell AVW1 Specifications download pdf (Page 44)

AM16/32B Relay Analog Multiplexer

'Deactivate Multiplexer

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'Call Data Table

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7. General Measurement Considerations

Long lead lengths – Longer sensor-to-AM16/32B leads result in

greater induced and capacitively coupled voltages (cross-talk)

between cable wires. To minimize capacitive effects CSI

recommends the use of cabling having Teflon, polyethylene, or

polypropylene insulation around individual conductors. You should

not use cables with PVC insulation around individual conductors

(PVC cable jacket is acceptable). It may also be necessary to program

a delay within the measurement instruction allowing time for lead

wire capacitances to discharge after advancing a channel, before the

measurement is made. Please consult the theory of operation section

of your datalogger manual for more information.

Earth Ground – The AM16/32B’s ground lug should be connected to

earth ground via an 8 AWG wire. This connection should be as short

as possible. The AM16/32B also connects to earth ground via the

datalogger. The lead wire that connects the datalogger power ground

to the AM16/32B power ground (“GND”) establishes this connection.

The Installation/Maintenance Section of your datalogger manual

contains more information on grounding procedures.

Completion resistors - In some applications it is advantageous to place

completion resistors at the datalogger terminal strips. Certain sensors

specific to the use of multiplexers are available from CSI. Examples

include soil moisture probes and thermistor probes. Please consult

CSI for ordering and pricing information.

Contact degradation - Once excitation in excess of 30 mA has been

multiplexed, that channel’s relay contacts have been rendered

unsuitable for further low voltage measurement. To prevent undue

degradation, it is advisable to reserve certain channels for sensor

excitation and employ other channels for sensor signals.

8. Installation

The standard AM16/32B may be operated in an indoor, non-

condensing environment. If condensing humidity is present or if the

possibility exists that the multiplexer might be exposed to liquids, a

water-resistant enclosure is required.

Several enclosures are available for purchase through CSI (models

ENC10/12, ENC12/14, ENC14/16, and ENC16/18). They offer a

degree of protection against dust, spraying water, oil, falling dirt, or

dripping, noncorrosive liquids. These enclosures contain a mounting

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