Product Spotlight

Two-Wire Transmitter -

Potentiometer Input

Our "sleeper" product - not new and, you would think, not particularly exciting, but people keep finding it and buying it, so we thought we'd feature it.

Pretty simple - takes a potentiometer input and converts it to a 4-20mA two-wire (loop-powered) output. Quite honestly, it was an afterthought when we designed our temperature (RTD and thermocouple) two wire transmitters years ago. Laying out the circuit board so it could also be assembled for potentiometer input was easy, so we included it.

Sells better than we ever expected. Just this month we picked up two new customers for it. The applications can be anything that needs to convert position to an electrical signal. A couple applications - level measurement and boat throttle position. The level measurement application uses a probe with series of resistors and reed switches, activated by a magnetic float.

Links: Model JH250 Potentiometer Transmitter
Other Two-Wire Transmitters
Our web site - http://www.jhtechnology.com/

Can You Help????

Here's a question we can't help with. Can you?

The other day a fellow called to ask if we could build a custom dashboard panel for his car. We've had two similar calls recently - at least one of them was from a man who was converting an older model to electric power. (He wanted it to look as much like the original dashboard as posssible.) All of them had seen from our web site that we can design panels and minisystems.

This is outside our area of expertise. Industrial control panels, yes. Automotive, no. We'd need to know the size, shape, mounting arrangements etc of the car's dashboard and the electronic details of the car's sensors.

I thought I'd post this for our readers. Can you help, or do you know anyone who can?

Product Spotlight

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Field Mount Enclosures

In our last posting (December 26,2009) we highlighted our FDT5000 Series field mount transmitters with displays. If you don't need a display you can mount any of our plug-in transmitters and alarms in the two enclosures featured here.

NEMA-4X Rated Enclosure

Splashproof & corrosion resistant, it includes the mating socket. It is normally sold without an opening or conduit connection as the installer usually prefers to determine this detail. If you would like us to provide this please e-mail jhtek@jhtechnology.com or call 941-927-0300 (in the US, toll-free 800-808-0300) us with your requirements.

Part #ENCL-1-8 with 8-pin socket, or ENCL-1-11 with 11-pin socket.

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Explosion Proof Enclosure

This is a Hubbell-Killark enclosure, modified by adding an 8- or 11-pin socket. UL, CSA and Factory Mutual approvals include Class 1, Div 1 & 2, Groups A, B, C & D when properly installed. A neoprene o-ring assures water-resistance per NEMA 4/IP66. Two 3/4 inch-14 NPT threaded conduit openings are provided.

Part #ENCL-EX1-8 with 8-pin socket, or ENCL-EX1-11 with 11-pin socket.

Product Spotlight

Field-Mount

Transmitters

with Displays

Designed for outdoor and other wet/dirty environments, our FDT5000 series transmitters feature:

• Splashproof/ Corrosion Resistant Enclosure per NEMA 4X
• User-Rangeable 3-1/2 Digit Display
• Wide Selection of Input Styles
• Voltage or Current Output Ranges
• AC and DC Power Options

For full information visit the Field Mount Process Transmitters section of our web site (www.jhtechnology.com/field_mount.htm).
If you don't need a display, we also offer NEMA 4X and explosion-proof enclosures for our plug-in transmitter and alarm modules.

Our home page: http://www.jhtechnology.com/

Signal Isolator Serves as Subtractor

Measurement and control applications sometimes need a difference (A - B) calculation. Examples include:

• Liquid level measurement in a closed vessel. Level is proportional to the bottom liquid pressure minus the top ambient (gas or air) pressure.
• Liquid blending control. Must maintain a zero difference between two measured flow rates.
• Relative speed control. Control for zero difference between two speed measurements.

JH Technology offers a complete range of multiple input add/subtract instruments, but when the inputs are voltages a lower-cost isolator may do the job.
The figure shows two voltages, both grounded. The signals may come from two pressure or flow transmitters, tachometers or other sources. The isolator's input is connected between the two positive voltages; thus, the input is (V1 - V2). Its output may be set to equal the differential input or it may be scaled up or down, offset or converted to a current signal such as 4-20mA.
We offer plug-in, DIN rail and field mount style isolators and transmitters.

Links: Add/Subtract Transmitter Modules
DIN-Rail style add/subtract transmitters
All Process Transmitters and Alarms

Simple Specials

CUSTOM

MODIFICATION:

TWO INPUT RANGES

Our OEM customer, who manufactures level control systems, wanted to be able to interface more than one type of level sensor with his system. Specifically, he needed to translate both 4/20mA and 0/5 volt level signals to match his system's input.

Our solution - a modified version of our JH4300 DC Input Transmitter capable of accepting both ranges. For 4/20mA the input is connected to pins 5 & 6. For 0/5 volts pins 4 & 6 are used, plus a jumper between two terminals. This avoids the need to stock two different types of signal conditioners.

More detail. Their level system normally uses a variable resistance level sensor. (In fact, they are a regular customer for our resistance input transmitters.) 4/20mA or 0/5V is only occasionally required, so they did not wish to redesign the system's electronics. Their original request was, could we translate 4/20mA or 0/5 volts to a 0/90 ohm resistance? The answer was no, this would not be a simple modification.

Instead, they determined and we verified that their electronics passes a constant 2.5 mAdc current through the sensor. Thus, 0/90 ohms translates to 0/0.225 volts. We set up our output for this range.

Conclusion: they now are able to work with several types of level sensors without modifying their system. All they need to do is connect the level sensor to our module and connect the JH4300's output to their system's input.

If you have similar needs, please remember that we can make "simple" modifications without large engineering costs or minimum order requirements. To contact us e-mail jhtek@jhtechnology.com or phone (800) 808-0300 (outside the US, 941-927-0300).

Links: Custom & Special Process Transmitters
JH Technology Web Site: http://www.jhtechnology.com/

Just for Fun - Hallowe'en 2009

HAPPY HOLIDAYS!!!!!

Created by Rick Maccani, our Technical Services Manager - with help from his wife.

For those of you who are "electronically challenged" the symbols are - - eyes=diodes, nose= capacitor, mouth equals resistor.