- The Dart3 has a 0-40V analogue input.
- The inputs are only accurate to within approx 100mV (0.1V).
- On the 12-way harness, this is the Orange/White wire, pin 6.
- The analogue input simply measures the voltage at the input.
- Generally, this voltage comes from a sensor, where the voltage is proportional to the sensor reading.
Examples of applications include:
- Fuel Level/Tank Level Monitoring
- Often an asset's fuel gauge will have a voltage output. The voltage seen is proportional to the fuel level.
- 0-5V Analogue Sensors
- Many sensors exist which output a voltage, i.e. 0V is the bottom of the range, and 5V is the top. These can be connected with no integration required.
- The sensor's range will need to be reviewed. If it has a large range, i.e. -70°C = 0V and 380°C = 5V, the analogue input may not be accurate enough.
- 4-20mA Sensors
- The 4-20mA (current) signal can be converted into a voltage via a sense resistor. Meaning these types of sensors can be read.
- Please note that analogue input draws current and can affect the reading. If high precision is needed, this device type should not be used.
Connect the Dart3 Orange/White wire to the +ve of what you are monitoring.
To simply report the voltage seen at the input to the server, no special configuration is required. The below is default, and the analogue input is mapped to Analogue Input 5 by default.
If the above is configured, the voltage at the input will simply be read approximately every 200ms while awake. However, there are no special logs based on the Analogue input - instead the current value at the time of other logs (i.e. heartbeats, elapsed time, start of trip, heading change during trip) is simply uploaded within analogue 5 at these times.
This means that the value is updated with each heartbeat when out of trip (default 60 min) and about every 60 sec when in trip.
Analogue Threshold Parameters
For some applications, we may want different upload behaviour compared to what is described above. For example:
- To save data/cost, scale back in trip logs + heartbeats, and force an upload if we breach the threshold at any time (rather than waiting for the next heartbeat)
- Upload if the fuel/tank level is dropping too quickly, and keep uploading regularly until it gets back to normal.
To fit use cases such as these we can configure the analogue threshold.
Example: Alert when Generator Voltage dips below 18V
- We are monitoring a generator, which our device is connected to. The Dart3 external power (red and black) is wired to the generator.
- The generator both powers the Dart3, but this external voltage is also what we are interested in measuring
- To save data costs, and platform fees, the heartbeat has been scaled back to once daily, and in trip uploads disabled.
- We want to be notified if the generator voltage dips below 18V, as this means it requires attention.
The image above shows settings to fit the use case.
- Analog Input
- Analog input 2 is the input used for Vext
- Check Interval
- Sample the input every 1 min to check for changes
- Enable Low Threshold
- We are configuring a lower bound threshold for an alert when we dip below 18V
- Analog input 2 is the input used for Vext
- Low Threshold Value
- 1800 = 18V
- High and Low Hysteresis
- 25 means that if the voltage dips below 18V, the threshold is breached, but it has to return back to above 18.25V to reset. This stops multiple alerts going off if the asset hovers about the threshold - i.e. flicks between 17.99V and 18.01V for exampleThe inputs are only accurate to within approx 100mV (0.1V) - so configure a hysterisis value above this.
- Upload on Event Start
- Yes = Upload as soon as we dip below 18V
- Action on Event End
- When we return back to 18.25V (back to threshold range) - upload again.
Analogue Value Conversion in Telematics Guru
- When using the Analogue Input, this simply records a voltage. We need to translate this into a meaningful value. i.e. tank level, temperature, pressure etc.
- The reading on the Orange/White wire is sent to the server in mV - i.e. 3000 = 3V
- We can convert the value by creating an I/O mapping.
- We have a level sensor which outputs 1V when the tank is empty (0%), and 5V when full (100%)
- This gives us (1, 0), (5,100) in terms of x and y coordinates.
- TG allows us to enter a conversion factor and offset
- We can use this to create an equation of the form y = mx + c
- x = voltage
- y = tank level
- i.e. the relationship between tank level from a given voltage.
- Handy calculator - https://planetcalc.com/8110/