RLE LD1500 V.3.1 - Manual (Page 21)

rletech.com LD1500 User Guide 21
3 Installation
3.5 Calibrate Cable Resistance
Distance-read leak detection systems are resistance-based. RLE’s orange water sensing cable
has a base resistance of 2.8 ohms/foot, while most other sensing cables, including RLE’s green
chemical resistant sensing cable, have a resistance of 4.0 ohms/foot.
The resistance of each length of sensing cable may be slightly more or less than the base
resistance due to manufacturing variances. For this reason, the cable length displayed on the
home page of the web interface may be slightly more or less than the actual length of cable
installed.
A system configured using base resistance values will still be very accurate. If you wish to fine
tune the resistance value of your LD1500 system to make it more precise, you may do so. This
will increase the accuracy of the system, and bring the LD1500’s reported installed cable
length value in line with the actual length of cable installed.
1 Ensure the LD1500 has been powered and has all the sensing cable attached to it, with no
alarms present.
2 Gather and record the following data from the home page of the web interface:
Record the resistance per foot setting, as reported by the LD1500. This can be found on the
Leak Configuration page of the web interface (Configuration > Leak Settings).
3 Note the actual (physical + simulated) length of cable physically connected to the system.
For your reference:
Record this sum:
4 Verify the current reading on the cable from your recorded values above. This value must
be less than 15 μA in order to calibrate the system. If the current is higher than 15μA, clean
the cable. Isopropyl alcohol works well to remove any contamination that might have
gotten onto the cable during installation.
5 To calculate the most accurate resistance value for the system, divide the reported cable
length by the actual cable length, and multiply the quotient by the reported resistance.
Cable Length (as reported by the LD1500)
Cable Current
Leg 1 Resistance
Leg 2 Resistance
Reported Resistance per Foot
♦ WCCS simulates 50 ft. ♦ XCON simulates 150 ft.
♦ SDZ simulates 50 ft. ♦ Nonsensing cable does not add
any length to a system
Actual length of cable connected to LD1500