SRQ Technology, Inc.

Signal Conditioners:

Process Transmitters & Alarms

As founder and former owner of JH Technology, Harry Trietley designed most of the signal conditioners (process transmitters and alarms) on their web site. Previous measurement instrument design experience includes Wilkerson Instruments, YSI (Yellow Springs Instruments) and the former Taylor Instruments.

So - what are signal conditioners? Simply put - devices that converts one type of electronic signal to a different one.

Now, that's a bit broad. You might consider televisions or compact disc players to be signal conditioners. After all, they convert their input signals into entirely different video or audio signals. The term, "signal conditioner", generally refers to industrial signal conversion instruments also known as process transmitters and alarms.

Transmitter? Until recently, process transmitters haven't "transmitted" over the air at all. (Some modern types now do.) Rather, they "transmit" or send their converted signals - analog or digital - over wires. In fact, the original process transmitters were not even electronic. Precision designs using bellows, nozzles and baffles, bourdon tubes and the like produced a variable analog pressure signal, typically 3 to 15 PSI (pounds per square inch), proportional to the measured pressure, temperature or other variable. Signal "transmission" was through tubing. These still are in use: they aren't affected by electrical noise and can't possibly touch off an explosion!

An industrial signal conditioner or process transmitter takes a measurement input, translates it to an acceptable control signal and sends it on to one or more "receivers". The receivers usually are control instruments or systems. You might liken it to an audio systems where the preamplifier takes a signal from a radio tuner, an audio tape, a compact disc or a record pickup (remember them?), amplifies it and sends it on to the power amplifier which drives the speaker.

Temperature control, for example, might start with the very low millivolt signal from a thermocouple. The signal conditioner amplifies the signal and performs other conditioning functions. A control device receives the amplified signal, compares it to the desired setting and tells the heating or cooling source to do more or less, or maybe just turn on or off. The system may also display or record the temperature.

Usually signal conditioners are processing slowly-changing signals, but some applications require fast or high frequency response. Click here to see our white paper on High Speed Signal Conditioners.

We've neglected alarms. An industrial alarm takes the same type of signal but simply compares it to a trip point or set point and gives a good/bad, hi/lo or on/off output. The output usually is an on/off contact closure or a hi/lo voltage.

Our measurement instrument designs have included process transmitters for thermistors, conductivity, dew point (lithium chloride sensors), dissolved oxygen and liquid level as well as the more-common measurements such as thermocouple, RTD (resistance thermometer) and strain gauge. We've also designed signal conditioners for power voltage, current and frequency inputs. These don't amplify; rather, they reduce and electrically isolate the input from the output before sending it on to the receiver.

We recently completed a dual-input digital signal conditioner whose output is computed from two sensor inputs. Details are on our Digital Designs page.

JH Technology's web site shows our broad background of standard signal conditioner and measurement instrument designs. Our claim to fame, though, is our specials capability. We routinely work with JH Technology to provide "simple" modifications to standard products at low cost and little or no added turn-around time. We've done:

  • Process transmitters with fast response, slow response, custom filtering.
  • Remotely located adjustments and other non-standard connections & set-ups.
  • Alarms with delays.
  • Non-standard input types & ranges.
  • Unique math functions such as:
    • (A + B) or (A x B) where A is a potentiometer and B is a voltage or current.
    • Math functions with unequal input ranges.
    • Absolute value function.
  • Peak-picker (fast rise, slow decay)

Feel free to contact either us or JH Technology.