User's Manual

301UM0031_01 TD136 Enhanced Vehicle Detector User Manual Page: 22 of 29
8.2 DU100 – DETECTOR DIAGNOSTIC UNIT
The DU100 Diagnostic unit is a hand-held test instrument that has been designed to operate with the
TD136 Enhanced Vehicle Detector to provide installation / service personnel with positive verification
of the correct installation and operation of the vehicle detector.
The following parameters may be verified using this instrument:
1. Detector type and version
2. Loop status Display of loop frequency and magnitude of current change of loop
inductance %∆L/L.
3. Frequency Readout of the actual loop operating frequency and the magnitude of
the frequency drift since the last re-tune.
4. Sensitivity Displays the Minimum and Maximum changes of Inductance %∆L/L that
caused a detect since the last re-tune.
5. Status Displays the current status of the detector i.e. Undetect, Detect, Open
circuit, Short circuit or Indeterminate.
6. Time The time in days and hours since the last re-tune and the reason for
the last re-tune i.e. Reset: manual or power failure, Loop short circuit,
Loop open circuit, Indeterminate or an Inductance change of greater
than 15 % ∆ L/L (typical)
This historical information is invaluable in providing information about
intermittent faults.
7. Crosstalk Allows for the comparison of the operating frequencies of detector
loops in close proximity to each other. If the operating frequencies are
to close the DU100 test will indicate a failure.
For further information refer to the Diagnostic Unit DU100 User Manual Document No. 895UM0001.
It is highly recommended that after installation of a detector (or if the loop has been changed in any
way) that the DU100 Diagnostics Unit is used to verify the correct operation of the detector. A record
of the readings should be kept so that if there is a problem in the future a comparison can be made to
identify what has changed. The form in Appendix A could be used to record these readings.
8.2.1 Interpretation of DU100 readings
8.2.1.1 Frequency
For the TD136 Enhanced Vehicle Detector the Minimum frequency is 12 kHz and the Maximum
frequency is 85 kHz
If a 20 µH loop is connected directly (no feeder cable) to the Detector and the Frequency
switches are set to “High Frequency” the typical frequency would be 84 kHz
If a 1500 µH loop is connected directly (no feeder cable) to the Detector and the Frequency
switches are set to “Low Frequency” the typical frequency would be 13 kHz
If the Frequency reading from the DU100 is close to the Maximum Frequency the inductance of
the LOOP is too small – you need to add turns to the loop