Search results

If you're a newbie and you're using the word 'hysteresis', you must have picked it up from something involved with this controller, so I'll propose that you have an on-off pressure controller. Every controller has a setpoint, which is the pressure value you want the system to be. The...

If you connect a HART communicator to a HART transmitter in a point-to-point current loop, the transmitter does what is always does - it converts the primary variable to a 4-20mA value on the current loop. - it responds to request(s) from the HART master, the HART communicator, for HART...

Unitronics issue with comm retries? RS-485 reflections from cabling's impedance mismatch? I notice the Hitachi uses an "RS45 modular jack" (apparently an an RJ45 connector carrying RS-485). Hitachi provides no internal termination resistors. Did you split apart the CAT cable to...

Sometimes you gotta bite the bullet and buy the book and you find out it pays for itself 20x over again. I'd recommend "Practical SCADA for Industry" by David Bailey and Edwin Wright. It answers the questions you're asking.

Do not locate the high and low side taps/ports at the 'top' of the pipe; do not locate them at 12:00. Instead, locate the taps/ports at 3:00 or 4:00 on the pipe circumference in order to avoid air/gas in the impulse lines. Probably be a good idea to use a 5 valve manifold so that you...

Valves are machined chunks of metal or plastic that don't talk Modbus. But the positioner or actuator that drives the valve might talk Modbus. A Google search for valve actuator Modbus will bring up a number of hits for actuators that talk Modbus. I suspect you're looking for a...

I could not enable a channel on an ISA100 wireless field transmitter until I had put the device into Out-of-Service mode (OOS). It would not accept the change while in operation. It might be something similar for your FF situation.

I know a number of controls guys who have programmed a PLC to run a motorized valve, but there are relatively inexpensive modules that take a linear voltage or DC current signal (like 4-20mA) and output the control signals to the actuator. http://api-usa.com/valve_positioner.php

The principles of operation for Fireye's UV flame scanner are explained in the opening paragraph: http://www.fireye.net/pdf/CU-22.pdf An amplifier and flame safety controller are typically separate electronic modules.

Siemens has a single channel ultrasonic level unit, the LUT400, which I saw a month or two ago. Its 4-20mA output is a new design; it can be either an active output, powered by the LUT, or a passive output, powered by an external DC power supply. The Siemens guy was with the local rep...

The first thing that comes to mind when you write, "When I try to poll input registers" is whether you mean that you are polling 3xxxxx input registers with function code 04. Does the Gateway support Modbus data on input registers? The Wireless HART gateway I saw put data into Holding...

1) A datum is missing - what is the expected DP range? It's a filter application, but is the expected DP across the filter 0.1 bar, 1 bar or 10bar? Is "dirty pressure drop bar VTA" supposed to mean something in this regard? It means nothing to me. 2) The pressure is getting up there...

Some comments on RS-485 or converters 1) I never use a port powered converter on a laptop because the serial port is not likely to supply sufficient electrical power for reliable use. Even on a desktop PC I will power the converter. 2) The labeling of RS-485 lines is all over the map...

Maybe you'd want to take some measurements, make a drawing and post it on site where it could be accessed? There's not a lot of incentive to pursue a VERY specific diverting valve only knowing that it's a diverting valve.

Q1. How do I know who is the master and which is the slave? Do I decide? Would DCS be the master or it does not matter? DCS usually has Modbus master capability. PLC's might or might not, it depends. A Modbus master is usually described as such. Devices lacking a a specific functional...

> Can i know, what will be the temperature reading in the DCS when Thermocouple burnout occurs? Not without checking to see a) if the burnout detection is enabled b) whether burnout is configured up upscale or downscale. For heating control loops, input burnout is upscale, which drives...

I don't know what 248 to 255 are used for. They're not used because that's what the Modbus spec says. Modbus Over Serial Line V1.02", page 8, Section 2.2 Modbus Addressing rules, "from 248 to 255: Reserved".

It isn't a Modbus master you're looking for, it's some other set of functions relating to what you're going to do with the data. You need to define what you need the software (that has a Modbus master) to do with the data from the flow totalizer. Save it? Print it? Trend it? Make up...

I suspect that a fuse installed in a 4-20mA loop is an attempt to protect an analog input on a 2 wire, loop powered circuit, and that the fuse is not there to protect the wiring. The fault condition that can damage a 2 wire loop powered analog input is a short between the two wires going...

My recommendation is to use a generic Modbus master, like Win-Tech's Modscan32 in order to be able to see reads from registers before and after the target register, to be able to see response messages that can tell you there's no connection or a time-out error, be able to make on-the-fly changes...