Search results

I have no idea what "node.readHoldingRegister" actually does but assuming that function reads Holding Register (4)0001, then a valid reply returning the value 227 would be interpreted as a pH of 2.27, as shown in the sample return message on page 7 of the manual, where for Register 0, the...

Another implementation problem with a really long RS-485 bus with lots of slave devices is ground loops causing comm problems. The RS-485 differential references signal ground, which can be isolated to the chip itself, but most commonly is not because non-isolated chips are cheaper. The...

1. No. Modbus slaves cannot talk directly to other Modbus slaves. A Modbus slave can only talk to the Master. A Master would have to be programmed to transfer data from slave A to slave F. 2. The functionality of 'controlling a slave' is specific to a slave's Modbus functionality...

It is not possible to "poll multiple devices simultaneously" over a single Modbus RTU RS-485 bus because the RULE of Modbus RTU is one master only, only one transaction at a time; not multiple transactions. The reply/response from a Master's query/poll must be received before another...

#1: I'm not sure what you're proposing. #2: I don't know what a "CLP" is. maybe PLC? Obviously, additional PLC(s) can service each smaller group of slave devices faster than a master can service a larger group of slaves. #3: Adding serial cards to a PLC is a typical approach for increasing...

I noticed you mentioned that the course is not on a fixed schedule. I had experience with both fixed and free scheduled learning. I completed a 'correspondence course' in the early '70's that involved receiving a text book, and then doing individual chapter lessons which needed to be mailed...

What does the COMM message say? What does the Siemens report when the Comm message is there, and when the COMM message disappears? Does the 4-20mA continue to operate? If not, what happens? Does it go full scale in one direction or another? Does it lock up when it should change...

How are they "communicating"? What does a communications failure look like?

Yes, the continuing 'number of polls and 'valid slave responses' indicates continued successful communication. It is my experience that most serial devices need to be power cycled before the device 'recognizes' a serial port setting change. Yes, once the Device ID is changed, you'd have to...

What you are looking at is the date/time stamped 'Traffic' display. It exercises your hexadecimal language skills. Change to 'Data' display: Setup > Display Options > Show Data

The Modbus function code 10 hex (16 decimal) is used to write one or more 16 bit value(s) to Holding Registers by the Modbus master/client. The master needs to have that Modbus function 16 (decimal, 10 hex) implemented. I can show how to first read the value, the write a value in Open...

You are sure that there is no soft starter driving the motor?

I have postulated the following reasons for intermittent spikes on RTD circuits over the years, but have never had anyone confirm a cause of intermittent RTD spikes. 1. break/fault in wire wound RTD element with intermittent connection 2. Intermittent induced noise through, untwisted...

All devices on the bus will have to have the same parity setting. Most slave devices's RS-485 ports are not isolated and many do not have a signal ground connection terminal (terminals for driver lines only). The RS-485 signal ground is frequently the chassis ground. Differences in ground...

Why do you suspect that the problem is in your code? Is the device powered up? Is the comm cable still connected? Is the comm network still functional, from one end to the other? Are there junction boxes en-route that have flooded or been damaged? Did the device get a firmware update? Was...

From the text on page 20 on using "a jumper between pins 6 and 8" for the last power meter, one can infer that the power meter uses Modbus RTU with an RS-485 electrical bus, not Ethernet. The power meter would be a Modbus RTU slave. A Windows Modbus Master/client (or an HMI program with a...

I think you need a decoder ring Joking, you need a proprietary protocol reference manual. If the protocol in question uses proprietary function codes then it's not Modbus, it's a proprietary protocol. There's lots of proprietary protocols. In the early internet days (late 1990's), a...

I have heard of leaking capillaries being repaired with the requisite vacuum evacuation and backfill by a reputable remote seal 'house'.

Not an email controllable device as far as I know, but a remote controlled relay connected via its web page has a function to control the output of the remote control "Web relay". https://controlbyweb.com/webrelay/

There's the possibility of a leak in the threaded fitting that allows fill fluid to leak or air to enter capillary.