Two Wire Transmitters

Some People Like

Trimpots!

We recently picked up a new customer who ordered a few of our 2-wire thermocouple transmitters. This customer sells thermocouples and other temperature probes, and the manufacturer they represent also offers transmitters from a well-knows European company.

Why did they buy ours? The European brand is computer-ranged. The end user wanted to be able to adjust calibration without needing a computer set-up. So, they bought our "old fashion analog" fixed range Model JH220 - complete with trimpots!

This is at least the second time this has happened. Another of our customers, a temperature sensor manufacturer, ran into exactly the same objection years ago and regularly offers our transmitters even though they also handle the European brand.

Do you need to change ranges but still like trimpots? Model JH225 (shown) adds switches that let you recalibrate to almost any practical range for thermocouple types J, K and T. (You do need a calibration source.) We also offer similar transmitters for RTD (resistance thermometer) sensors.

Links:
Model JH220, thermocouple 2-wire transmitter, fixed range (factory set)
Model JH225, thermocouple 2-wire transmitter, user-rangeable
Model JH240, RTD (resistance thermometer) 2-wire transmitter, fixed range
Model JH245, RTD 2-wire transmitter, user-rangeable

All 2-Wire Transmitters

Fast Response

Speedy!

OK - maybe you're expecting me to promote our fast response to your orders. (Sneaky how I worked that in!)
The real topic - fast-responding signal conditioners.
A few months ago a customer asked if we could provide frequency response to at least a few kilohertz for DC and load cell signals. Our standard circuitry could not. His quantity requirements were large enough that we designed a new circuit to meet his needs (3kHz minimum). We've since shipped his order. He tells it is working well in his application - heavy-duty shock testing. More recently another customer needed just three fast-response units which we now are able to easily supply.
We're working on the paperwork and documentation to turn this in to a standard catalog product line of DIN-rail mount transmitters. Look for it shortly.
Meanwhile, if you have high-frequency or fast-response requirements, please ask us. E-mail jhtek@jhtechnology.com or call (800) 808-0300 (US toll-free) or (941) 927-0300.

Link to Fast Response Process Transmitters

Thermistors for Temperature Measurement

Thermistors for industrial temperature measurements? Sure - we just took a repeat order from an OEM customer (for instruments - we don't sell the thermistors themselves). So, I thought I'd write about them.

Let me identify myself - Harry Trietley, President & Chief Engineer. In the 1980s I worked at YSI (formerly Yellow Springs Instruments) who had once pioneered precision interchangeable thermistors. (They no longer make them - sold the product line off.) So, I had the opportunity to learn how to apply them. We now have two regular OEM customers.

You won't find thermistor info on our web site - maybe we should add it. For now, this blog is a start.

Thermistors are resistance thermometers but much different from RTDs (Resistance Temperature Detectors). RTDs are linear (approximately), wide range, relatively low sensitivity (about 0.4% per deg C) and increase with temperature. Thermistors are highly nonlinear, narrow range, high sensitivity and decrease with temperature (about 4% per deg C).

There are many types of thermistors - small, large, highly accurate, loose accuracy, many shapes. This blog is about NTC (Negative Temperature Coefficient) thermistors. There also are PTC (Positive Temperature Coefficient) thermistors that act more like thermal switches - increasing resistance rapidly in just a few degrees near the switching point. PTCs are not used for linear temperature measurement.

Precision NTC thermistors excel in moderate temperature, narrow range applications. They are very sensitive, and some have tighter accuracy specs than RTDs. One of our customers uses them in heating/air conditioning control; the other, precision measurements related to integrated circuit manufacturing processes. They also see wide use in medical and laboratory temperature measurement.

We have made simple adaptations of our signal conditioners (temperature transmitters) for use with thermistors. So far we haven't published standard spec sheets, but they are very similar to our other instrument styles. (See http://www.jhtechnology.com/).

If you have an application let us know. Each application is different as there are many thermistor types. We would need to start by knowing your measurement temperature range - also the thermistor type if you have chosen one yet. If not, we can help you find the right one. Probably best to ask for Harry.

e-mail: jhtek@jhtechnology.com, US phone (941) 927-0300 or toll-free (800) 808-0300.