Simple Special: Y = 1/X

Our customer needed a simple mathematical inverter: Output = (Constant) x (1/Input). Our standard product line includes analog division.

We simply disconnected input A and tied it internally to full scale.

The key requirement was that the user properly specify the input/output relationship. (Note that at 0% input the output would be 1/0 = infinity.) This application required:

Input = 1 volt, Output = 5 volts

Input = 2 volts, Output = 2.5 volts

Input = 5 volts, Output = 1 volt

Mathematically this is: Output = 5 / Input.

We tied input A to a fixed internal voltage and set the instrument's gain appropriately.

JH Technology offers add, subtract, multiply, divide, square and square root functions in plug-in modules, DIN-rail transmitters and field mount transmitter/displays.

http://www.jhtechnology.com/

True RMS Measurement Includes DC

Simple Modifications meet Customer's Needs

When measuring AC voltages, DC components or offsets usually should be ignored. Examples include measuring AC ripple from a DC power supply, and data or audio signals superimposed on DC power lines. As shown in the figure, a blocking capacitor removes any DC component.

Therm-O-Link, a wire manufacturer in El Paso, uses rectified but triac-modulated power in their annealing operation. To monitor and control the annealing process they need to know the total voltage, DC plus AC. They also need true-RMS measurement for accurate power monitoring regardless of the waveform.

A simple modification to our true-RMS process transmitter, Model JH6010IR, removed the blocking capacitor for full DC response. Additional changes speeded the transmitter's response time for proper operation in their control system.

For the complete application note, True RMS: AC or DC Response?, click here.

True RMS Measurement Basics

RMS measurements express the power capability of an AC source. Low-cost meters and transmitters often make a simpler average measurement rather than true RMS. The two are not the same, and the relationship between average and RMS measurements varies for different waveform shapes. The figure shows a pure sine wave, a chopped and rectified sine wave and a square wave pulse.

True RMS measurements require more complex and expensive circuitry, generally available in slightly higher priced instruments.

To learn the fundamentals of RMS measurement click for our application note, What is True RMS - and When do I Need It?


JH Technology manufactures:
Plug-In True RMS AC Process Transmitter
DIN Rail Mount True RMS AC Process Transmitter
Field Mound True RMS AC Transmitter with Display
Plug-In AC Alarm Trips with True RMS Response

Our web site: http://www.jhtechnology.com/

Why We Like "Small" Customers

You've probably heard the old "80 -20" rule - 80% of (xxxxx) come from 20% of (yyyyy). As applied to marketing, 80% of your sales come from 20% of your customers; therefore, you should focus the bulk of your efforts on the 20%.

Well, of course, we do pay attention to our larger customers, but we work just as hard to meet the needs of new and small users. Why? First, it's in our nature, but its also good for business. Here's our favorite success story.

In 2001 an engineer named Mike Sanders found us and asked if we could meet a special need - a 2-input load cell (strain gauge) transmitter. That's not one of our standard products, and he only needed a couple, but we found a way to modify our standard strain gauge transmitter (Model JH4051) to meet his needs. Small order, but we did it.

Jump forward to December 2002. Mike called us. He'd joined another company, Wave Biotech, who made mixing and packaging equipment for the pharmaceutical industry. Their product included four load cells and he had ideas which could improve it. His needs included the ability to accurately sum either three or four load cells, to choose either of two output ranges, adjustability/rangeability per specific requirements, and filtering - just enough to smooth the signal while maintaining a reasonably high response speed.

We built a quick prototype. He tested and liked it. We finished the design and laid it out on a circuit board to fit a cavity in their machine.

The result? They became our biggest single customer (in dollars). GE bought the company and moved the operation to Sweden in 2008. During the move we worked with them to improve EMI/RFI specs. They're still our customer and their orders remain as strong as ever.

Here's a link to their "how it works" page.

The US operation closed, unfortunately, but we still hear from Mike.

Here's a link to our Customs and Specials page. What can we do for you?

Our main web site (signal conditioners): http://www.jhtechnology.com/

Thermocouple Application Note

Unusual Thermocouple Application

Our customer's client had a large spa facility. The controls had been located near the spa, but the client felt they should be moved to a more benign environment, several hundred feet away. The system included four thermocouples. Sending thermocouple signals this distance is expensive, since thermocouple wire (not copper) must be used. Even more basic, sending weak millivolt signals hundreds of feet leaves them subject to interference and signal degradation.

To boost the signals, four standard thermocouple transmitters (our Model JH4130) were added near the spa. Their 4-20mA current signals easily traveled the distance with no degradation. The system designers opted not to change the control system, so it was necessary to convert the current signals back to their original thermocouple voltages. "Reverse" thermocouple transmitters, 4-20mA input, thermocouple output, were needed.

We provided them. We modified our Model JH4300 DC input, DC output transmitters to have the proper millivolt outputs. The most interesting challenge was, the millivolt outputs needed to be connected to thermocouple wires (not copper) for proper connection to the system's thermocouple inputs. This called for the reverse of cold junction compensation (we called it "cold junction un-compensation"). A temperature sensor embedded in the output terminals and some properly-designed circuitry solved the problem

Temperature Transmitters & Signal Conditioners - our web site: http://www.jhtechnology.com/

Custom Designs

A Very Special Special

A well-known company needed to duplicate a thermocouple alarm they had bought from Action Instruments decades ago. Action was no longer able to provide it so they turned to us.

Action's original "Action Pak" line (Action's trademark) once included alarm modules with extra options such as retransmitting outputs and remote setpoint inputs. 20-pin headers (pin bases) were required to provide the extra connections. As far as we are aware these headers are no longer available.

Our customer's requirement was a nonstandard version of one of those alarms. We replied that we could provide the same function but with a different connection arrangement. This was not acceptable - it was for a nuclear power application and they could not vary the system design. Only one piece, but they were willing to pay for it.

Once again we got lucky. In 1995 we had purchased some 20 pin headers for another customer's need and had a handful left. Our customer bought one (couldn't convince them to buy a spare) - even sent an inspector to Florida to do a source inspection. That was 2008. In 2009 they again bought one and just now ordered two more! Possible future problem - after this order we have only five headers left.

(Note: We do not sell nuclear-approved products. This alarm was sold as "standard commercial quality" for a noncritical application.)

Technical detail: the custom alarm module has two retransmitting 0-1V analog outputs, one proportional to temperature and the other proportional to the setpoint. Our customer was able to supply us with Action's specifications and we designed it to be functionally identical. Here's the functional diagram.

If you have special requirements let us know. Phone (941) 927-0300 or toll-free (800) 808-0300.

E-mail jhtek@jhtechnology.com.

Link to our page on Custom & Special Signal Conditioners.

Signal Conditioners, General - our web site: http://www.jhtechnology.com/

Current Booster

THE BOOSTER!

Well, ok, not that booster!

Another "rush" special - to boost the current drive from a voltage signal. Our customer needed -10 to +10 volts to drive a 50 milliamp load. The voltage output from their control signal could supply only a fraction of that, so they needed an output-equals-input driver or current booster. They called us.

• 
  
  Additional needs: "ASAP - yesterday if possible" because they had just discovered the system problem.
• 
  
  Very high accuracy for their test application.

We got lucky. Years ago we solved another customer's high-current requirement by designing a custom circuit board. The requirements were different, but we were able to use that board to assemble the required circuit. It so happened that we had three of those boards left. Our customer needed four, but two could wait. We received the order March 22, shipped the first two March 23 and ordered a few more boards from a quick-turnaround service.

Accuracy? We guaranteed +/-3mV on a 20 volt wide span (+/-0.015% of range).

The customer has now asked us to quote on an 8-channel version.

This one isn't on our web site, but you can see examples of other special & custom signal conditioners at www.jhtechnology.com/customs.

Simple Specials

Standard Product, Nonstandard Connections

Our OEM customer needed a fully compatible replacement for a thermocouple alarm module they once bought from England. Our Model JH1200 plug-in thermcouple alarm filled the bill, except the pin connections were different.

The answer was simple - take our standard product, unsolder the internal wires from the pins and rewire them to be the same as the British product. And, since the the connections to the thermocouple were changed, we also needed to relocate the temperature sensor used for cold junction compensation.

One more step - we made a simple adapter to allow the converted alarm module to plug into our standard production test and burn-in fixtures.

This customer buys only one or a few at a time, but they've become a regular for several years.

Links: Process Alarms
JH1200 Thermocouple Alarm
Custom & Special Signal Conditioners

Simple Specials

SPECIAL ORDER -

SUM THREE UNEQUAL FLOWS

Flow #1: Full Scale (20mA) = 1.75 MGD (Million Gallons per Day)

Flow #2: Full Scale (20mA) = 22 MGD

Flow #3: Full Scale (20mA) = 1.04 MGD

Module Output: Full Scale (20mA) = 24.79 MGD

Something we do all the time - modify our products to meet out-of-the-ordinary needs. In this case the customer needed to add signals from three flowmeters, each having a different scale factor.

A bit of engineering calculation, followed by the selection of a few precisely-measured input resistors, did the trick.

One piece order. Turn-around time - four days from order entry to shipment.

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/

Special Modifications

Rapid Increase, Slow Decrease

("Peak Picker")

We've done this for a few customers. The basic application - monitor the peak value of a repetitive signal.
The first application was on an automated machine which formed nail heads. We never saw the machine, but our understanding is that it would "whack" heads on the nails in rapid succession. The user needed to know and control the impact force - not each and every individual impact, but the "normal" or "average" impact. In other words, he needed to know that the machine was properly set.
As the sketch shows, the output rises quickly to the peak value but decays slowly. (Actually, the unit we built had more filtering than is shown in the illustration.) The output of our module smoothed and held the value of the peak impact force.
We've built a few variations on this theme. One had an adjustable decay time (reference - our special feature #X0098) and one had a fixed 3-second time constant (X0214). Right now we're quoting a unit which adds a polarity-insensitive "absolute value" function - both positive and negative peaks will produce a positive output.

Links: Custom & Special Signal Conditioners
Our complete signal conditioner line

Special Modifications

Slow Increase, Rapid Decrease

Just the opposite of the "peak picker".

Application - Heating oven control.
The customer wanted to avoid rapid temperature increases and overheating and so wanted a "slow" filter on the control input. On the other hand, he required a rapid turn-off for fast shutdown. We were able to modify our transmitter's input stage to accomplish this.
(Reference - our special feature #X0251.)

Links: Special & Custom Signal Conditioners
Our complete signal conditioner line

Absolute Value Function

Absolute Value -

with a difference

(Details on the application mentioned in our September 27 posting.)

A new customer had an urgent need for a signal conditioner (transmitter) with absolute value response. Searching the internet, he read our "Specials & Customs" page and found that we had done this before. His need was different, but we were able to help him.

For those of you who may not be familiar with the absolute value function, it simply ignores the minus sign. The previous special which he found on our web site took a -10 to +10 volt input and created a proportional 0 to +10V output. For example, inputs of either minus 7V or plus 7V created a plus 7V output.

The new customer's application needed a signal representing the temperature deviation from ideal. Ideal temperature produced a 12mA current signal. A deviation, whether positive or negative, required a positive-going output (see graph). At 12mA input the output should be zero percent (4mA). At either 4mA and 20mA (8mA deviation) the output should be 20mA (100%).

We were able to modify the earlier special to accomplish this. As mentioned in our Sept. 27, 2009 post we did some Thursday evening calculations, quoted and took the order on Friday, built 6 units on Saturday (yes - we added an expediting charge) and shipped Monday.

Let us know what we can do for you!

Links: Custom & Special Signal Conditioners
Our home page: http://www.jhtechnology.com/

Fast Response - Part 2

Speedy - Part 2

(See August 16 for Part 1)

Part 1 announced fast-response instruments. This time we're promoting our fast response to customer needs.

Thursday afternoon: We received two urgent calls, two different customers, asking "can you do it" and "how fast"? One was for 10 pieces of a standard product; the other, 6 specials which required modest new circuit design. We were able to say "Yes" to both.

Friday morning: Received both orders.

Friday evening: Two of us (Rick & Harry) stayed late.

Saturday: Rick & Harry worked from about 8:00 until 2:45PM. Finished both orders.

Monday: Both orders shipped. (Of course, both customers paid expediting charges to cover our overtime.)

Details: The standard-product order (JH4001I RTD Transmitters) was from a Navy base. They had been using "Brand A" products but that company was not able to delivery quickly. They sent searching and found us on the web. We did not have any in stock either - so we worked the weekend!

The special requirement was for an absolute-value transmitter. (See our posting of October 3, 2009 for more detail.) We had done this before (as a special in 2001) but the detailed requirements were different on this time. Thursday evening calculations plus weekend assembly and test got the job done.

Conclusion: If you need action, call us.

(800) 808-0300 or (941) 927-0300. e-mail jhtek@jhtechnology.com