NovaLynx Corporation
225-RHP-2Sxx
Page 7
January 2021
7
TROUBLESHOOTING
If the sensor’s output signal appears to be in error or is absent, check the power connections. At the
sensor cable, measure the battery or the input power source voltage with a voltmeter. Be sure that the
instrument has been powered up correctly or wait for the next power ON cycle to occur. Check any
batteries to be sure that they have sufficient charge and an adequate voltage level to power the
instrument and that all connections are secure. Inspect the battery terminals to ensure that they are
clean and solidly connected to the battery.
7.1
Troubleshooting 4-20 mA Models
Verify appropriate supply voltage. The transmitter requires a minimum of 10 and a maximum of 35
VDC at its connection for proper operation. Choose a power supply with a voltage and current rating
which meets this requirement under all operating conditions. If the power supply is unregulated, make
sure voltage remains within these limits under all power line conditions. Ripple on the supply should
not exceed 100 mV.
Loop Resistance – The maximum allowable loop resistance depends on the power supply voltage.
Maximum loop voltage drop must not reduce the transmitter voltage below the 10 VDC minimum.
Maximum loop resistance can be calculated with the following equation. Vps is the power supply
voltage.
Some receivers, particularly loop powered indicators, may maintain a fixed loop voltage to power the
device. This voltage drop must also be subtracted from the power supply voltage when calculating the
voltage margin for the transmitter. The following equation takes this into account. Vrec is the receiver
fixed voltage.
7.2
Troubleshooting 0-5 V Output Models:
Verify appropriate supply voltage. The 0-5 V output requires a DC supply of 15-35 V or an AC supply of
15-29 V for proper operation maximum. Maximum output load is 5 mA.
7.3
Determining the Source of a Failure
The sensor is one part of the measurement system, and it is possible that the logger or PLC that the
sensor is being used with is actually the cause of a problem. If the problem cannot be located using the
