NATA Facility Calibration Instructions
These instructions are intended for a NATA calibration facility but the same techniques can be applied by any user with the appropiate calibration equipment.
It’s imperative that the LoRaWAN gateway supplied by Telemetry2U is powered up, connected to the internet, and within 100 meters of the sensors before commencing as the gateway is the bridge between the sensors and Telemetry2U’s IoT platform. The gateways internet connection can be made via ethernet or through Telstra’s 4G network (SIM card usually supplied and pre-fitted to the gateway). You should receive an email when your gateway connects to the internet successfully.
The nodes should already be linked to the calibrators account and visible on the reports page linked from the main top menu. The nodes name, or “node description” can be broken into 4 parts that represent the nodes unique “Dev EUI” (found on the sticker on each node), the sensor(s) that require calibration, the verification/calibration points, and the required calibration tolerance. For example, a “node description” of
A8 40 41 40 23 45 64 68| EXT+INT | -30,0,30 | 0.3
indicates a node marked with “Dev EUI” A8 40 41 40 23 45 64 68 requires both the internal and external sensors to be calibrated (or verified) at -30C, 0C and +30C and pass within 0.3C. A list specifying all the details should have been provided by Telemetry2U to cross check before proceeding.
Nodes are shipped powered off to save battery life and will need to be turned-on to acquire current readings. There are generally two types of nodes supplied by Telemetry2U, and both have different power-up procedures and calibration limitations/requirements as explained below.
Dragino LHT65 with internal and External Temperature Sensors
- Power-up procedure: Hold “ACT” button in for 5 seconds
- Power down procedure: Press “ACT” button 5-times quickly
- Internal Sensor Resolution: 0.1C
- External Sensor Resolution: 0.1C
- Stabilisation Time: 1-Hour
- Temperature Limits: -40 to 85C
- Expected Accuracy: 0.5C
Once powered up, the LED should flash green once it has sucessfully conected to the network. Upon sending, the LED will blink red if no external sensor is installed and blue if an external sensor is installed. You will need to plug in the supplied external sensor if that is the sensor to be calibrated. Be sure to push the connector firmly to ensure a proper connection.
***Please note that neither sensors on the LTH65 are waterproof so the calibration will need to be performed in a enviromental chamber
Dragino LTC2-xx with External RTD Temperature Sensor
- Power-up procedure: Rotate jumper to short pins
- Power down procedure: Remove jumper and place over 1-pin only
- External Sensor Resolution: 0.01C
- Stabilisation Time: 1-Hour
- Temperature Limits: -200 to 200C
- Expected Accuracy: 0.2C
Fit the supplied antenna to the external SMA connector to ensure adequate signal strength.
Upon power-up, the Green LED should blink briefly followed shorty after by a 2-second blink indicating that it has successfully connected to the network.
The RTD sensor is waterproof and should be calibrated in a waterbath to obtain a better uncertainty.
Within 10 seconds of powering up, the node(s) should have sent an updated record to Telemetry2U and will continue to do so every 2-5 minutes until the node is powered down. The node(s) time stamp on the main reports page should now have updated to the current time. It will be necessary to refresh the page manually to retrieve the most recent record(s) on a regular basis.
The LHT65 has three sensors, internal temperature, internal humidity, and external temperature sensor. They are labelled "Int. Temperature", "Int. Humidity" and "Temperature" on the reports respectively. The LTC2-xx has only one temperature sensor that is simple labeled "Temperature".
The calibration procedure can now be started. Program the environmental chamber or water bath as required and place the sensors in the calibration environment and leave to stabilise for at least 1-hour for each calibration point. You can review the real-time data from the reports page if necessary but remember to refresh the page
Once the multi-point calibration cycle has completed, all the temperature data should again be visible on the reports page. You can use the date and time stamp for each record to compare against the reference thermometer used during the calibration. Please match the sensor time and the reference sensor times as closely as possible to get the best calibration results. If all points fall within the specified accuracy (0.3C for the LHT65 and 0.2C for the LTC2-xx), the calibration check is complete and not further work needs to be done. If they fall outside the specification, a calibration will need to be applied and the sensors checked again.
The calibration can be applied via the calibration page found under Admin>>Calibrations. Telemetry2U currently allows for a 2-point and 3-point calibration. See the example calibration entry form below.
To enter calibration data, select the device from the ‘Node’ dropdown box. Again, this will be identified by the DEUI on the device sticker as described earlier. Enter the name of the company, accreditation number, and site number in the ‘Calibrated By:’ field. Enter the calibration certificate number in the notes section if available at this time.
On the sensor that is being calibrated, select ‘3-point’ from the calibration type field. Remember that ‘Int Temperature’ is the devices internal temperature sensor and ‘Temperature’ is the external temperature.
In the ‘Uncalibrated readings’ field, enter the three raw sensor values recorded on the reports page from lowest to highest, separated with a comma (,). In the ‘Calibrated readings’ field, enter the respective reference sensor reading in the same format, lowest to highest and separated with a comma (,). All data points should be entered with two decimal places (0.00). Once you hit the ‘Save’ button at the bottom of the page, you should observe a change in value in the ‘Current calibrated’ field at the end of the line. The calibration will be applied to all data from 00:00(12am) onwards.
Be sure to power down the devices as soon as the calibration has been completed so ensure to save excessive drain on the internal batteries. Instructions on how to power down each sensor was explained above.
Enter all recorded temperature calibration data on the calibration certificate and fix a calibration sticker to both the side of the node and also the external sensor (if applicable). This completes the calibration process.