Cable Length Extensions for Probes and Communication Cables

This article describes the criteria for extending the cable length of A-series Current Tranducers , ET-series Temperature Probes, EH-series RH & Temperature Probes, Thermocouple Wires and Communication Cables.

ET Series Temperature Probes

These Temperature probes use a thermistor sensor – the resistance varies with temperature. Since conductors have an inherent resistance, there is a limit to the length of cable that can be added to a thermistor probe without affecting readings. The maximum recommended length is 100ft (30m) of 2-conductor 22-gauge stranded wire ACR C/N 31-0007. Use shielded cable and connect on on the Data Loggers end to the Common terminal along with one of the conductors. Use Quick Connect splices to connect the wires ACR C/N 18-0019. WARNING: Not suitable in vicinity of high temperature of ET-081 and ET-086.

EH Series RH & Temperature Probes

These Relative Humidity and Temperature probes use capacitive and resistive sensors. Since the conductor’s capacitance and resistance are proportional to length, there is a limit to the length of cable used. The maximum recommended length is 100ft (30m) of 4-conductor 24-gauge stranded cable with a shield ACR C/N 31-0006. ¬†Replace the 3ft (0.9m) cable using a flat blade jeweler’s screwdriver connecting the shield to the Common terminal of the Data Logger.

Thermocouple Wires

These Temperature sensing wires generate voltage proportional to the temperature differential from either end of the cable. The maximum recommended cable length for the 20 gauge T/C wire is 300ft (100m). It is not recommended to use regular cables in extending thermocouple wires. The extension wire should be of the same type (K, J, etc.) as the sensor leads. Using any other type of wire will introduce a thermocouple junction. Measurement errors are caused by thermocouple junctions.

IC/LIC-102 Interface Cables

The IC-series Interface Cables may be extended with as many as ten CB-020 20ft (6m) Extension Cables to a maximum recommended length of 200ft (60m).

What is the maximum Cable length between a Computer and a Data Logger?

It depends on the type of computer port and quality of cable. For a Data Logger to wake up and work properly, (when you open the Connection to start communication), there has to be at least 4.5VDC present between the tip and base of the plug at the Data Logger end. If communication proves unreliable, simply reduce the Baud rate thru software. Up to 3 SmartReader Plus Data Loggers can be attached with a Modular Cable system up to 1000ft (300m) w/o a Power Supply.

Testing the Communication Cable after Extension

Open the communication port and use a voltmeter to check the voltage between the tip and base of the plug at the Data Logger. If the voltage is below 4.5 VDC, add a Y-Adapter (YA) and a Power Supply (PS) to boost the line. For Stereo Cable systems, purchase YA-200 C/N 01-0098 and PS-201-EU C/N 01-0164 or PS-201-NA C/N 01-0165 for 220VAC or 120VAC respectively. For Modular Cable systems, buy PS only.