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I haven't seen the use of a "page number" before, but the formula is similar to an industrial wireless gateway's register addressing. The wireless gateway collects data from multiple wireless field nodes. Each node has 32 registers. Each node has a node ID number, 1 - 32. All Modbus data...

I've heard that the EIA RS485 standard says A is negative and B is positive, but it doesn't really matter what the spec says, we all have to deal with reality which is that some manufacturers label the lines one way, others label the lines the opposite way. Since A is supposed to be the...

Modbus is responsible for packing binary bits into a specified format and transporting them from slave to Master or vice versa and for generating some basic error codes in the case when transport part doesn't happen as expected. The interpretation of the received data is up to the...

question: > how to discriminate slave 1 of first server from slave 1 of second one? Answer: >3 Slaves each with its own IP address A unique IP address is used for each slave.

You should try the on-line current loop circuit calculator (in the post above), it's pretty cool. http://www.divize.com/techinfo/loop-voltage-calculator.html According to its calculation for - a 24Vdc power supply - 300m of 1.5mm2 copper wire (3.63 ohms) - a 250 ohm receiver load...

The Experion PKS (R430) is a DCS. Honeywell requires registration to get access to DCS material, other than 4 color marketing brochures. I don't know what their registration acceptance criteria is.

Thank you for your observations. Very interesting Modbus derivative. Would you mind sharing some information for those who might run into the same situation? What brand and model Flow computer is this? Which Function Code is accomplishing this 20 word read of historical values? FC...

The imposed limitation of 'reading one individual entry at a time' of 'historical data' with 'FC3' doesn't make sense to me. The standard Modbus Function Code (FC) 03 has a 2 byte field for a starting address and a 2 byte field for quantity of registers. FC 03 addresses data in the 4xxxxx...

1) I'm not a generator guy, but I have to believe that the specific point that tripped the high alarm has to be in an error/fault log somewhere. That should point you in the right direction as to which sensor circuit to investigate. 2) An RTD high alarm is caused by a higher resistance at...

I only quoted GE's spec. I'm not a GE guy, so the interpretation partially mystifies me, too. However, I've done remote thermocouple CJ with a Honeywell HC-900 PAC. Honeywell's method of using a remote sensor might have some similarity to GE's method, although Honeywell uses a 100 ohm Pt RTD...

The spec sheet for the GE Versamax IC200ALG630 T/C card here, http://tinyurl.com/hptj9vh on page 5 under cold junction compensation says, Cold Junction Compensation: The Thermocouple module provides four choices for Cold Junction Compensation. - No Cold Junction Compensation: This is...

> "The two devices do communicate" Do you actually successfully read or write a value? Or do the Tx/Rx LEDs blink? What constitutes 'communication' in the current state? > "no parity and 2 stop bits" A number of masters and slaves can't handle 2 stop bits, even though it's part of the...

Correction (the word NOT is missing above) >The HART communicator does provide a reference temperature >or a reference pressure. Should be: The HART communicator does NOT provide a reference temperature or a reference pressure.

Control Engineering, a trade magazine, ran an article http://www.controlengeurope.com/article/91592/Smart-devices--configuration-or-calibration-.aspx that succinctly spells out what a HART communicator does - configures a field device, according to the quote below. "<b>Configuration</b>...

> The DC power <snip> is going and coming back within a split second. How do you know this is the case? Do all 24V powered controls 'blink' momentarily as power drops?

You need to ask the thermal dispersion flow meter's manufacturer what the implication of a formerly properly operating flow meter now reading a clearly false negative process temperature is. But I'll venture a guess that the design calls for a failed temperature sensor circuit to go to a...

Interesting point about open circuiting the AO, Steve. In 35 years of dealing with single loopers/PLC/PAC AO's or panel meter re-transmit AO's I can't recall an AO that was ever damaged by "open circuiting" it. The firmware driving the AO, however, is very likely to complain and squawk...

That was a great description of the problem; somewhat unique in ForumLand. I had similar circumstances - when the laptop was 'floating' on battery power it worked fine. When the laptop charger was plugged in, the 485 network essentially had a heart attack. I put in an RS-485 isolator...

> Does an ungrounded thermocouple works the same as an isolated thermocouple? Yes. > In my project, I'm reading a grounded pot. If "pot" is a potentiometer, that is a variable resistor, not a thermocouple. It is likely isolated, but will not generate an EMF on its own. If "pot" is a...

1) I once ran 2 wire loop powered transmitters' loop current through a relay. Any momentary open circuit would trip the transmitter into its initialization routine when DC power came back, even milliseconds later. The initialization routine left the loop without a PV or a false 4.0mA PV until...