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Yes. Typical commercial flame detectors use lead sulfide (PbS). The photo sensitivity and dark resistance of PbS changes as the element temperature changes requiring temp compensation, but even temp comp is typically limited to 50°C (125°F) at an upper limit. Recommended installation...

> Got a project coming up that requires a honeywell udc temperature controller to > be connected via modbus TCP/IP and an noe card to a modicon quantum plc. The UDC talks Modbus over ethernet. I can't help you with the Modicon side. In general, for Modbus comm with a Honeywell UDC here's...

Can I assume that a 2 wire analog input is a conventional 4-20mA analog input? If so, you need to look for a 2 wire, loop powered "temperature transmitter" that handles an RTD input (some models are thermocouple only input). There are hundreds of manufacturers of such. The transmitter...

That was worth a star just for the ASCII artwork. The wiring confuses me, too. Thanks for posting what it is, though.

> Can any body tell how this drift happens What you already listed: ambient temperature, meter body temperature, humidity all affect instantaneous readings. One manufacturer's reference conditions are stated as 25°C (77°F), 10 to 55% RH. Chemical reactions at the wetted diaphragm can...

Flame Safety is typically a separate, agency approved control circuit that includes a flame sensor and controller whose output drops out fuel blocking valves.

200 page Getting started manual, here: http://www.chem.mtu.edu/chem_eng/current/new_courses/CM4120/2009/Getting%20Started.pdf take out any space that the forum inserts into the URL

A 2 wire loop powered instrument uses about 3.5mA from the signal line to power itself and do whatever it needs to do. So loop powered instruments can never be 0-20mA because at least 3.5mA (or thereabouts) are needed to run the instrument. A running 'loop' that is not in fault mode...

There are commercially available thermally conductive epoxies (google will find them) Although I haven't seen ever seen anyone use baling twine, I have seen these used to secure an RTD to the outside of a pipe: hose clamp, wire, RTD wedged under steam heat trace pipe/tubing, epoxy, plumber's...

The whole point of using thermocouple extension wire is to bring the "cold" junction back to where it can measured so that cold junction measurement can be used for in the cold junction compensation calculation. Yes, one can make an assumption about what a remote cold junction temperature is...

I agree with your assessment of how close Pt100's are to their tables. But I've worked with the pharmas and seen their accumulated cal paperwork that shows that RTDs can drift over time. Maybe you've got a baddie. Some other thoughts: In the absence of model info, I looked at the...

Just to clarify, a Type K thermocouple does NOT use copper wire as extension cable. Even a Type T thermocouple which is composed of copper alloys does not use ordinary copper wire as extension wire, it uses type T extension cable. The extension cable must match the type thermocouple to...

From National's AN-1057 note on RS-485 https://www.national.com/an/AN/AN-1057.pdf Generally, a shield connects to a solid ground (normally, the metal frame around the system or subsystem) with a low impedance at one end and a series RC network at the other. This arrangement prevents the...

Can we assume that this is a rehash of your earlier thread? http://www.control.com/thread/1340882905 It appears that you are now using Modscan (a generic Modbus master app) rather than writing your own driver (calculating your own CRC?) Before we get into modbus comm details, why do you...

The comments were made on a discussion in the LinkedIN Foundation Fieldbus Users Forum Group: http://www.linkedin.com/groups/I-was-wondering-if-you-79953.S.122863916 (take out any spaces the forum inserts into the URL)

Thank you, Mr. Berge, for that clear and concise explanation. I'll go back and look for the LinkedIn discussion link.

I am only familiar with a field device's output (not an analog input) being classified as active or passive, where active outputs are powered from field device's power but passive outputs are powered from a power supply external to the field device, as in a 2 wire, loop powered output that uses...

You might consider looking at Applied Instrumentation in the Process Industries by Andrew and Williams. It is a 3 volume set, the 3rd volume is reference tables and resource material. The first edition was mid 1970's, 2nd edition early 1980's, so they're somewhat dated, but many aspects of...

The orifice plate bore is sized at specific 'design' conditions to produce a certain max DP at a certain max flow rate, for instance, 4,000l/hr at 100"w.c. DP The orifice plates from our vendor are stamped with the manufacturer's name, a serial number, an inlet bore size in inches to 4...

At a local ISA meeting about a year ago, I sat through a typical power point slide presentation on the benefits of FF, all aimed at reduced wiring costs. OK. Since I have to keep things running in the plant, I naively asked the same question as the OP and got the same brush-off, "I don't...