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How do I set the digital outputs of the controllers via Modbus protocol commands?

Fri, 13 Apr 2012 12:28:00 GMT

There is no dedicated commands to set digital outputs via Modbus in a direct way. To set these outputs (I/O 1, I/O 2, I/O 3, I/O 4 and I/O 5), a little trick is necessary: you must configure the alarms in a condition they will certainly activate. It follows an example on how it can be accomplished to I/O 1 (relay 1) and a K type thermocouple.

Set I/O 1 = 1 (it associates the output to the alarm 1)
Set SP.A1 = -150 (configured as the minimum possible reading of the sensor)
Through a Modbus command:

Set Fu.A1 = Hi (write value 5 on the address 35): this command activates the output unless the thermocouple is really reading -150 �C (if this is the temperature you are reading, you have to set a "Lo" alarm with a high set point).
Set Fu.A1 = OFF (write value 0 on the address 35): this command deactivates the output.

You can control the other alarms outputs in a similar way.

What are those values I must assign to the digital filter?

Fri, 13 Apr 2012 12:27:00 GMT

The digital filter implementation in this product makes that, on each new input signal sample (A/D conversion of a certain channel), the conversion outcome is updated with the difference between the previous result and the new sample value divided by the filter value.
The filter accepts values ranging from "0" to "20". The "0" value means that no filter must be used and the conversion outcome is always the result from the last sample. From that filter value on, the bigger the value, the bigger the divider, which makes the new samples to have a smaller weigh in the outcome composition.

Can the communication link quality be altered?

Mon, 09 Apr 2012 16:40:00 GMT

In the case of AirGate-Modbus it is possible to see that attenuations can occur when obstacles are put in the way where the signal path is, but the communication link will be lost in case AirGates are already operating at a limit distance.

Can I use other antennas in AirGate-Modbus?

Mon, 09 Apr 2012 16:39:00 GMT

Yes, AirGate-Modbus has a female RP SMA (plug) for the antenna, the same used by the majority of the WiFi routers. Any antenna that connects to that plug and has operation specifications in the 2.4 GHz band with 50 ohm impedance can be used. If the communication link between the AirGates is not good, there are three possible solutions for solving the problem:

Use a pair of AirGates as a repeater; (How can I increase the length between AirGates?)
Use an extension cable to better locate the antenna; (I have an AirGate-Modbus placed inside a closed electrical panel, which is diminishing the communication between the Airgates. How can I improve this link?)
Use antennas with a bigger gain.

For applications inside buildings, we recommend the usage of omnidirectional antennas. For open-field applications, where there is need for interconnecting two points, it is advisable to use directional antennas. A research with companies specialized in antennas can show the best antenna for your application.

I have an AirGate-Modbus placed inside a closed electrical panel, which is diminishing the communication between the Airgates. How can I improve this link?

Mon, 09 Apr 2012 16:34:00 GMT

When an AirGate-Modbus gets into a misplaced location related to the rest of the network, as in a closed panel, it is advisable the usage of an extension with a magnetic base in order to improve the antenna position. On repositioning the antenna, making it having a line-of-sight to the rest of the network, the communication link will be enhanced.
This extension cable is supplied as an AirGate-Modbus accessory by Novus. It is 2.5 m long and has a magnetic base for easy installation.