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About modbus protocol
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I don't know what 248 to 255 are used for. They're not used because that's what the Modbus spec...
Request for help related to appropriate hardware-software interface
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It isn't a Modbus master you're looking for, it's some other set of functions relating to what...
Why 250mA fuse for 4-20mA analog input?
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I suspect that a fuse installed in a 4-20mA loop is an attempt to protect an analog input on a 2...
Howto read Modbus registers to a HMI
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My recommendation is to use a generic Modbus master, like Win-Tech's Modscan32 in order to be able...
Network control of 4-20ma output
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I've used the WebRelay, and the people who make it have a catalog of control-via-web stuff.
But...
A colleague used a Red Lion Data Station Plus (DIN rail mount control module with serial and...
ModBus Plus
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4-5 years ago I stopped by the Modbus booth at the national ISA show.
I told the booth guy that...
terminating resistor
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This 7 minute video on youtube, Reflected waves on a cable, shows the distorted waveform on an...
Our process control systems are run by PLCs and have manual backup panel mounted in the control room. The OEM has gone to a semi- computerized MBU.
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I've heard that the US nuclear power industry is served by some companies that reverse engineer and...
Turbine flowmeter reading much more than should be
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> maybe there was something wrong with the mechanical transmission between the turbine and the...
Measurement errors in Allen Bradley MicroLogix RTD cards
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I've had to 'calibrate' one PAC controller (not an AB uLgx) at its working temperature in its very...
RTD PT110 and PT10 connection to DCS RTD Module in Yokogawa Centum VP.
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If your existing analog input module does not support either
- your types of RTDs, or
- generic...
Temperature compensation for density variation of air in hydrostatic measurement
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FYI, a year ago, maybe two years ago, a forum topic involved diminishing air pressure in a closed...
MODBUS Address - how to identify?
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The Modbus Standard Modbus over Serial Line V1.02 (downloadable for free at Modbus.org) says:
...
Slave Device does not respond to the master.
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2 wire RS-485 is implemented differently from manufacturer to manufacturer.
Although you might...
Problem with energy meter using modscan
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1) Have you tried looking at more than one data format?
2) Have you tried reading from another...
Proview - modbus - plc
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The link below is to a Chipkin's "Modbus for Field Technicians" document that covers...
Flange type DP Transmitter zero error
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What is the "top side" connection"? dry leg? wet leg? capillary with a diaphragm...
Can you recommend a book about instrumentation and process control in a petrochemical plant and oil and gas
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A frequent control.com contributor, Walt Boyes, is author of an excellent instrumentation book,...
Material For preparing Hook up drawings
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You can read Liptak's comment on loop diagrams for smart instruments here:
...
Key term:
Instrument Loop Diagram
...
Bearing Temperatures hunting
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Installing Instrumentation on Insulated Bearings
...
from the Instrumentation Engineering department...
Is there any difference in signal transmitted in HART and Fieldbus or not?Is there any difference in signal transmitted in HART and Fieldbus or not?
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http://iamechatronics.com/notes/general-engineering/294-h1-foundation- fieldbus-physical-layer...
use of neutral extension wires in industrial temperature measurement
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Curt,
Those L&N's you remember are probably not that much different from the one on display...
Neutral extension leads (as described in "Temperature Measurement", 1999, CRC Press)...
I hope not many, but I have seen it.
If by "neutral extension wires" you mean that...
Not getting real values and rapid changing Modbus reading from Allen Bradly PLC
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The data in the slave/server (presumably data in the PLC?) is in a format that has to be...
For example, what reading do you expect?
As examples, what readings are you getting that do appear...
Incorporating Pyrometers into an assembly line
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I guess it depends on the complexity of the pyrometer and what the intention is.
Is the...
Why are my Rosemount 3100 Level transmitter readings seem wrong (Lower than expected) even when my tank level is high?
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If the readings are always low, then the reference level point and the bottom level points are...
from the Instrumentation department...
Does the reading of a differential pressure transmitter change if we use a capillary tube?will the reading of a differential pressure transmitter change if we use a capillary tube?
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It depends on whether you have one remote seal on an open tank or two remote seals on a closed tank....
If you have two remote seals, one at the bottom with another one at the top, then you can move the...
Theoretically, the fluid in the capillary should transmit the pressure the same as tubing.
But...
Need you opinion on this topic: Minimum voltage for Hart communication
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It's Ohms Law.
To drive the same current through greater resistance requires a higher voltage:
...
The vendor assertions about minimum voltage are indeed correct. What you've missed is the minimum...
Suggestions for Obsolete panel meter replacement
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In the US, those are known as 1/8 DIN panel meters which designed to fit in the same panel cutout...
On a system consisting of a SLC 5/04 and a Panel View 1000, we want to display a running total from Signet Flow transmitters...
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Just because the previous posts are a decade old, does not invalidate them. Same situation today...
Possible issue with WX compensation cable to DCS reading of Thermocouple temperature?
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A 5°C error (maybe greater) is possible with some handheld digital thermocouple thermometers...
I could not communicate with my PC when i connected the MM LDM 7835 to my PC
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Assuming your software actually talks through a serial port, you need to check
- Windows'...
How does a motorised control valve works?
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It's not a problem if one is clairvoyant, but I'm not.
Some MOV's use 4-20mA input.
Some...
A major American manufacturer or two cannot provide wiring diagrams without the device's serial...
about compensation cable info reqirements
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Thermocouple extension cable is required because it completes the measurement, which is the EMF...
Pin Configuration for 25 pin RS232/RS 485 pin
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If the information is available anywhere, it's probably in the S9000 Communications reference...
When using HART COMMUNICATOR to interrogate the transmitter while carrying out PM or CM, HART COMMUNICATOR displays "NO COMMUNICATION".
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Four things are needed for HART communication:
1) a HART enabled transmitter
2) a DC power...
What is the error if you use a Tx cable with a K thermocouple?
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Just how much extension wire that needs to be replaced is involved here? A couple hundred feet?...
Oops, I stand corrected. In my earlier post, I was thinking ordinary copper wire was the...
Here's my rationale on the topic:
I don't think the error is a linearity question related to...
Explanation for extended modbus
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The question is about 5 bit (4xxxx) or 6 bit (4xxxxx) addressing.
One earlier thread (Aug 27,...
Range of Pressure Transmitters
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Everything effects 'accuracy'. Everything like temperature, aging, line pressure, hysteresis. So,...
What is the best way to connect Modbus TCP/IP wirelessly to a Siemens building management system or SCADA system?
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A modem converts one communications medium to another, like in the old days, a PC's binary RS-232...
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