304UM0001 Rev 00
PD160 Enhanced Series User Manual
Page: 15 of 39
3.2.5.3
Output polarity
The relay output polarity may be toggled between fail-safe and fail-secure via the relay menu.
In fail-safe, the output is the same in detect as it is with no power applied to the unit. Related to an
access control situation, this is used in situations where the loss of power must not lock people out.
Either a valid detect situation, or a power failure / fault will provide a signal.
In fail-secure, the output is the same in un-detect as it is with no power applied to the unit. Related to
an access control situation, this is used in situations where the loss of power must not allow people
free entry. Only a valid detect situation will provide a signal.
If installed correctly, the normally open contacts should be open in the event of no vehicle over the
loop and closed for a vehicle present over the loop. Units supplied with relays set to presence by
default are wired as fail-safe relays. Relays set to pulse by default are wired as fail-secure relays.
If the state of the output when the detector is off is not of concern, the polarity function can effectively
be used to flip the output logic on that relay.
3.2.6 Diagnostics
Users familiar with the DU100 from the PD130 range will find similar
features in the on-board diagnostics facility. The PD160 Enhanced
Series detectors are constantly monitoring their operation and
providing diagnostic information. Additionally, statistical information
such as the min and max values and the number of vehicles counted
are provided.
The following parameters may be verified using the diagnostics:
•
Loop status – Display the actual loop operating frequency and magnitude of the current change of
loop inductance %
∆
L/L as well as signal and noise levels.
•
Sensitivity – Display the minimum and maximum changes of inductance %
∆
L/L that caused a
detect since the statistics were last cleared.
•
Channel counts – Display the number of vehicles detected.
This historical information is valuable for providing information about intermittent faults. It is highly
recommended that after installation of a detector (or if the loop has been changed in any way) that the
diagnostics 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 C could be used to record these readings.
The sub-menus for diagnostics are as follows:
The frequency sub-menu shows the current frequency in kilohertz as
well as the individual max and min. The frequency is inversely
proportional to the inductance, so low inductances will show high
frequencies while high inductances will show low frequencies.
Depending on the frequency setting, the displayed values could be
from 12 to 80 kilohertz in the 20 to 1500uH range.
The sensitivity sub-menu shows the current percentage change in
inductance. Detects are shown as negative values and anti-detects
are shown as positive values. The max value will show the largest
percentage change noted while the min value will show the smallest
peak value of any one vehicle detected.
