Instructions

UM-0085-B09 DT80 Range User Manual Page 337
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For example,
6DSO(R,100)=1 6DS(W) DELAY=500 6DS
will output a 100ms positive going pulse on 6D, then tri-state the output, wait 500ms then read the state of 6D (which is
presumably now being driven by an external logic device).
 Sleep Mode
The states of all digital outputs are maintained while the DT80 is asleep. Note also that the RELAY output uses a
latching relay, so no extra current is required to hold it in the closed state.
 Power Loss
If the DT80 loses all power then all outputs will revert to their default state, including the RELAY output. If the
MAINTAIN_OUTPUTS profile setting is enabled then the outputs will be restored to their former state when power is
restored.
 Alarm Digital Actions
One or two digital outputs can be configured to follow the state of an alarm. That is, when the alarm is inactive the
output(s) are in their default state (1 for 1..4DSO, 0 for 5..8DSO, 1RELAY and 1WARN) and when the alarm is active
the output(s) will be in their non-default state. Alarm Digital Action Channels (P85) for more information.
 Delay Accuracy
The actual pulse width generated by the Delay option for DSO will not necessarily be exactly as specified. For delays of
20ms or less it will be close (within 1ms). For longer delays the resolution is +/- 16ms however it is guaranteed that the
duration will be at least the specified time.
The
PT (precise timing) channel option may be specified to force a precise delay time, even if the duration is greater than
20ms. For example:
1DSO(PT,500,R)=0
will generate a 500ms +/- 1ms duration pulse. Note however that during this time all logger operations including
communications, display updates and sampling will be suspended.
Note: Performing long delays using the Delay option is not recommended as it can prevent the timely evaluation of other schedules.
This is true regardless of whether the
PT option is specified.
Counters – Low Speed
The digital input channels 1D-8D can also double as low speed counter inputs (up to 25Hz).
The
C (counter) channel type returns the number of positive-going transitions seen on the specified digital input (1D-8D).
For example the channel
3C will return the number of pulses seen on digital input 3D.
The counter value is a signed 32-bit integer.
Any of the digital input wiring configurations can be used. That is, either contact closures or logic pulses can be counted.
Channel Options
The following channel options are applicable to low speed counters:
• the channel factor specifies a counter "wrap value". The counter will reset to 0 (or "wrap around") when this
value is reached. For example, if 8 pulses are received on input 4D then channel 4C(3) will count in the
sequence 1, 2, 0, 1, 2, 0, 1, 2 so after 8 pulses the value 2 will be returned.
•
R (reset): Counter will be cleared to 0 after returning its current value.
Using Low Speed Counters
 Scan Rate
The digital input channels are scanned at approx. 20ms intervals (50Hz). This means that for low speed counter
channels:
• the minimum input pulse width is 20ms – shorter pulses may not be recognised.
• the maximum input count frequency, assuming a 50% duty cycle, is 25Hz.
Use the Counters – High Speed (P338) for higher count frequencies.
 Sleep Mode
Digital inputs are not scanned while the DT80 is asleep so any transitions which occur during sleep will not be counted.
Use the Counters – High Speed (P338) if you need the logger to continue to count pulses even while asleep.