Ampcontrol Pty Ltd
– ABN 28 000 915 542
HPB USER MANUAL
HPBB012 Version 9
– March/2020
Uncontrolled Copy - Refer to Ampcontrol Website for Latest Version
Page 38 of 61
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16.1 Pilot Fault Finding Information
To carry out tests on a faulty earth continuity circuit adopt the following procedures:
Open Circuit Pilot
Check the voltage between the pilot and earth at the HPB Relay (Pins 6 and 7). The reading should be
30VDC.
To determine the location of the fault continue the above test along the pilot until no reading is obtained.
Current Check
Connect a DC ammeter between the pilot and earth at the HPB Relay (Pins 6 and 7). The reading
should be 45mA at the HPB Relay or at any point along a continuous pilot.
Repeat this test at the machine end of the pilot. If the voltage is normal (30VDC) but the current is less
that 45mA then the loop resistance may be too high.
Tests in Resistor Mode
When Resistor Mode has been selected, the pilot is terminated with a 235
Ω resistor. The voltage
measured across the resistor should be 10.6VDC.
The voltage measured at the HPB Relay will vary depending on the amount of resistance in the pilot
earth loop. For example, if the loop resistance is 100
Ω then the voltage at the HPB Relay will increase
by 4.5 volts (100 x 0.045) resulting in a reading of 15.1VDC.
Tests in HTU Mode
When HTU Mode has been selected the pilot is terminated with a HTU-1 Termination Module. The
voltage measure across the Pilot and Earth terminals of the module should be approximately 20VDC.
The voltage measured at the HPB Relay will vary depending on the amount of resistance in the pilot
earth loop. For example if the loop resistance is 100
Ω then the voltage at the HPB Relay will increase by
4.5 volts (100 x 0.045) resulting in a reading of 24.5VDC.