Daviteq 0-20 mA current input
MA
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1. Introduction
Overview
Daviteq 0-20 mA current input (MA) node to connect to 0-20mA DC current from Process instruments like Pressure transmitter, Temperature transmitter, Level transmitter, Flow meters, Analyzers... at very low voltage drop. The MA node can be integrated into the wireless transmitter from Daviteq, such as Sub-GHz WS433, LoRaWAN WSLRW, and Sigfox WSSFC, to build the complete Wireless 0-20 mA current input node. The MA node is also powered by the batteries or external power. The MA could ouput voltage to supply power for 0-20 mA sensor
Specification
Measuring range: 0 .. 20mA
Accuracy: 0.05% of span
Resolution: 1/3000
Temperature drift: < 50ppm
2. Principle of Operation
With ADC module, the MA node transform the 0-20 mA input from sensor to digital value
The MA Node could work in loop powered sensor or non-loop powered sensor based on wirings and configuration
3. Calibration
The MA Node is calibrated by following steps:
Note out the current coefficient A and constant B. A and B is in formula: Y = A *X + B where X is raw value and Y is mA
Set the coeffiecent A=1 and constant B=0 to the MA node memory
Connect the calibration current source to the MA node
Set the calibration current source to a low value ( 0mA ) and note out the X1 value
Set the calibration current source equal to 20mA and note out the X2 value
Calculate A, B based on formula:
0 = A*X1 + B and 20=A*X2 +B
Write calculated A, B to the MA node memory
Set alibration current source 0mA and 20 mA and check the value output to make sure the A, B is written properly
4. Application Notes
5. Installation Notes
Recommend using the shielded cable with twisted pairs;
Avoid the installation near by the high magnetic field like high power Motors, Transformers, and Power Generator.
Following right wiring connections based on 0-20 mA sensor
Note:
DO NOT CONNECT AN EXTERNAL POWER SUPPLY TO THE PWR + WIRE OF THE WIRELESS SENSOR !!!
SUPPLYING AN EXTERNAL POWER SUPPLY TO THE SENSOR'S PWR + LINE CAN MAKE SERIOUS DAMAGE !!!
4. Following wiring label as below
6. Troubleshooting
The output value is always zero
The sensor cable is broken
No 0-20 mA sensor is installed
Loose connection between the MA node and 0-20 mA sensor
The 0-20 mA sensor is defective
The MA node is defective
High cut setting is configured to 0
The output value of the MA Node sometimes fluctuate when mA input is unchange
Loose connection between the MA node and 0-20 mA sensor
The 0-20 mA sensor is defective
The MA node is defective
7. Maintenance
There are no moving parts or consumed parts in the MA Node. Therefore there is no need to do maintenance.
However, depending on the installation environment, the MA Node must be checked periodically for accurate ADC converter.
8. Default Configuration
This MA node has the default configuration, however, those parameters can be changed. The user can change the configuration on the wireless transmitter so that the complete node(converter+ wireless) delivers the proper output value. Please check the Payload document for more information.