DT80 Range Digital Inputs
From dataTaker Wiki (FAQ)
What can I use the Phase Encoder inputs for?
Phase encoders can be used for accurate measurement of shaft rotation, direction, speed and position. For example the position of a rotating assembly could be monitored in degrees or the position of a roller door monitored via the motor shaft rotation. This allows very accurate monitoring of position from drive components rather than direct measurement of the driven part.
DT80 & DT85 will support 2 phase encoders allowing XY position logging.
DT81 & DT82 will support 1 phase encoder only, so can only monitor a single axis.
What does ‘Open Collector’ and ‘Active Drive’ mean?
Two different digital output types are used on the DT80 range loggers. The Open Collector or Open Drain type is suitable for connection of relays etc and requires an external power supply. The Active Drive type is a TTL logic level output that requires no external power supply. Active drive can be used for input to other devices such as PLCs.
|Example: Open Collector connecting relays.||Example: Active Drive connecting PLC.|
How do I connect additional relays to the DT80 range loggers?
The simplest way to connect relays is to use the open collector digital outputs 1D-4D (DT80/85) or 1D-3D (DT81/82) with an external power supply. You can use the 12V output on the DT85 as the power source for the relays (just remember to turn it on with the 1SSPWR=1 command)
If further relays are required they can be connected to the Active drive (TTL) digital outputs 5D-8D (DT80/85) or 4D (DT81/82).
How do I connect the digital outputs to TTL input devices like a PLC?
Are digital and relay outputs maintained when the logger goes to sleep or loses power?
When the logger enters low power sleep mode, by default, all digital outputs and the relay output maintain the state they had prior to sleeping.
The relay is a latching type, which means that no additional battery power is required to hold it in the closed state.
If all power to the logger is lost (ie. there is no external power and the internal main battery is disconnected or flat) then all digital outputs will revert to their default states (for outputs 1D-4D the output drivers will be off, for 5D-8D the outputs will be tri-stated, and the relay output contacts will be open). This will also occur following a hard reset (SINGLEPUSH).
If you wish to have the digital states maintained over a reset then configure the profile setting:
Profile StartUp Maintain_Outputs=Yes
Note For DT80s produced prior to around March 2007, the relay output may not automatically return to the open state when all power is lost. This means that when power is restored, the initial state of the relay may in fact be closed, even though if you query the 1RELAY channel it returns 0 (open). Furthermore, due to the nature of a latching relay, it will remain closed, even if you enter 1RELAY=0.
If you find that the relay comes up in the closed state following loss of all power, you can force it back to the correct state by setting the relay closed (1RELAY=1) then open again (1RELAY=0). This can be done in a single command using
which will set the relay closed for 20ms then reset it back to open. From this point on the relay should work normally.
What is the maximum frequency of the High Speed Counters?
Inputs 1C and 2C (Selected by the HSC command) have a maximum input
frequency of 10kHz and a maximum input voltage of +/- 10V
Inputs 3C and 4C (Selected by the HSC command) have a maximum input frequency of 10kHz and a maximum input voltage of +/- 30V
Note the maximum input frequency for the high speed counters is 10kHz when driven from 5V TTL signal, higher input frequency can be measured when driven with a higher input voltage.
Counter input channels 1C-2C and 3C-4C have different electrical characteristics. In particular:
- Inputs 1C-2C include selectable TTL or low-level input thresholds.
Low thresholds (selected by using the LT channel option) allow direct connection to sensors whose output is only a few mV, eg. inductive-pickup flow sensors.
- Inputs 3C-4C use a standard TTL level Schmitt trigger input.