Just for fun

AFFORDABLE HOUSING!

Just for fun - actually from 2005 when house prices were escalating upward.

Our good friends in Charlotte had just signed for a new townhouse in Fort Mill, South Carolina. They took us to see the construction site and this is what we found on their lot.

Minisystem Controls Blending (Flow) Ratios

A very simple "system", but it solved our customer's problem.

The need: our customer needed a simple way to control the blending proportion (ratio) between two pump flows. The user desired a ratio adjustable from 1:5 to 5:1, with the center of the adjustment range being 1:1.

The pump controller's input was a standard 4-20mA dc control signal (4mA produces zero flow, 2o mA produces maximum). Our system needed to take the input (flow #1), multiply it by the ratio and produce an appropriate 4-20mA output (flow #2).
The solution: our JH4410 multiplier module plus a 10-turn precision potentiometer. The JH4410 was modified so that input B was the potentiometer's position. (Input A was set up for standard 4-20mA input.) The output's 4-20mA signal was proportional to input A multiplied by the potentiometer position. Additional modifications created the desired dial settings - 1:5 (gain = 0.2) at zero turns, 1:1 at five turns and 5:1 (gain = 5) at 10 turns.
At the customer's request the system was mounted in a wall-mount industrial enclosure.
For other examples of our custom & Minisystem solutions visit www.jhtechnology.com/customs.

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.

Split 4-20mA Loops without a Loop Splitter

Save money! Don't buy a loop splitter if you don't need one.

Users often specify dual-output 4-2omA current loop splitters in their systems. Common reasons include:

• The need for an output boost to drive several loads at once.


• The need to run independent isolated current loops to two different systems.
  

These needs often can be met with a less-expensive single-loop isolator. The diagram shows the basic idea - use the source transmitter to drive the isolator's input plus the first loop, then use the isolator's output to drive the second loop.
















For our complete application note (pdf) click here , or visit http://www.jhtechnology.com/ and click on the Application Notes link.

Hello, visitors

We've only just begun .... A brand-new blog.

JH Technology, Inc. is an electronics company - we manufacture instruments known as signal conditioners, used mostly in industrial measurement and control applications. What is a signal conditioner? It's an amplifier for measurement signals. Signal conditioners amplify and convert signals such as temperature measurement (thermocouples, resistance thermometers and thermistors), pressure, force and weight (strain gauges, load cells), position (potentiometers), speed and RPM (tachometer pulses) and others. We don't make the sensors themselves, but we amplify and convert their signals.

We're a small, engineering-driven company and have strong capabilities in specials and custom or OEM products. We're also a bit old-fashioned - we answer the phone instead of running you around in circles with voice mail. We're proud of our customer service. If you need application assistance, have odd requirements or just need fast delivery, give us a try!

More "blogging" to come. Meanwhile, if you're interested, please visit us at http://www.jhtechnology.com/. To learn more about our specials and customs capabilities, visit www.jhtechnology.com/customs.

Of course, feel free to call:

Toll-free in the US (800) 808-0300
(941) 927-0300.