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I purchased DAQ several weeks ago and I am still puzzled on setting up my channels. I can tell that this software is a quality product and can do far more than I need. I just need help getting one channel setup up to use as a reference to create more channels.

I am good on the setup of:

channel name, device type, i/o type.

my device is using Modbus RTU protocol. Its a power meter. It is configuered correctly and shows rx and tx.

All I need the software to do is read data which I understand is Fn 03.

One of the channels I want it to read is Line voltage.

The doc that came with the device says:

the address for Line voltage is


How do I input this address into daq? I am guessing that the address and chn # are the same.

thanks for helping, once I get one channel reading data, I will be able to create my other channels.


Other helpful info that might help you, help me.

I'm using ethernet connection.

The Modbus RTU protocol is used for communication


There are several rules to follow in using the meter:

1. Data type:

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Well, first you have to create a modbus device:

1) Click on Quick Device Configuration, select New Serial / Ethernet device

2) give the device a name ("Modbus" perhaps), add a new ethernet port and select Modbus RTU

3) In the channel table, you'll select this device. For D# you'll likely want 1, but its whatever modbus ID is assigned to your device. For I/O type, you'll want Read Holding, then presumably one of the Float types. You'll probably have to try each one until you get a valid number.

4) Channel # is the tricky part. The values you specified 400a/400b are hex values, not decimal. Modbus has a weird logical addressing scheme that is used by some manufacturers where the 4 in the beginning indicates a holding register. The 4 is not actually in the modbus query frame (and in fact the command is 3, go figure). This notation, however, is usually in decimal and its in the 40,000 range, so 40,001 is the first holding register and the frame actually has 0. In your case, it is unclear if the 4 in the front is the same indicator, or a real register. So, the channel number either needs to be 16394 which is the decimal equivilent of hex 400a, or simply 9, which is the decimal equivilent of hex A minus 1.

Basically you just have to try the different combinations until one works. There are only a few different combos, so it should take long. Once you figure it out, you can then apply whatever logic the manufacturer used to any other tags you want to read.

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