Honeywell Stainless Steel Pressure Tranducer Applications

These questions will determine whether you need a flush-diaphragm device and what materials can be in contact with the media. Honeywell's Data Instruments division manufactures some models with flush diaphragms and others with pressure ports. Both have stainless steel diaphragms in contact with the media so that many corrosive media will not cause problems.

What pressure will the transducer measure?
Your first consideration is the maximum pressure of your system. Normally you will want to use a transducer that has a maximum pressure range of 1.5 times the maximum pressure in your system. We advise this extra capacity because many systems, especially hydraulic and process control, have pressure spikes or continuous pulsations. The spikes can be five to ten times over the "maximum" pressure. These high pressure short duration spikes can destroy a pressure transducer. Continuous high pressure pulsations, near or slightly above a transducer's rated maximum, can also limit the life of the transducer. However, specifying a higher range transducer is not always a solution because you will sacrifice resolution. You can use a snubber to reduce the spikes, but this is also a trade-off in that it slows the response time of the transducer.

All of our transducers have been designed to withstand more than 200 million full pressure cycles with no loss in performance. Consider the system pressure carefully when choosing a transducer. You will be trading off system accuracy versus life of the transducer.

What is the pressure media?
Another key factor you must consider when selecting a transducer is the medium it will measure. Is it a viscous liquid or a slurry that could plug a pressure port? Is it a solvent or corrosive that could attack the transducer's materials in contact with it or is it clean dry air?

These questions will determine whether you need a flush diaphragm device and what materials can be in contact with the media. Honeywell's Data Instruments division manufacturers some models with flush diaphragms and others with pressure ports. Both have stainless steel diaphragms in contact with the media to reduce problems caused by corrosive media.

How accurate does the transducer need to be?
Accuracy is a general term used by many transducer manufacturers to describe the measurement error or uncertainty in the transducer's output. Sources of these errors may include nonlinearity, hysteresis, nonrepeatability, temperature, zero balance, calibration and humidity effects. Most manufacturers, including Honeywell's Data Instruments division, specify accuracy as the combined effects of nonlinearity, hysteresis, and nonrepeatability. For many transducers, "accuracy" errors are less than those due to zero balance or temperature. The "terminology" section explains these terms in greater detail. Higher accuracy transducers generally cost more. Does your system truly need this higher accuracy? Using a high accuracy transducer with a low resolution measurement instrument creates an ineffective solution.

What temperatures will the transducer see?
Pressure transducers, like all physical measurement systems, are subject to error or failure from extreme temperatures. There are usually two temperature ranges specified for a transducer. They are the operating and compensated ranges. The compensated range is a subset of the operating range.

The operating temperature range is that temperature range over which the transducer can be exposed while energized and not suffer damage. However, it will not meet its published performance specifications (temperature coefficients) when subjected to temperatures outside the compensated temperature range.

The compensated range is typically a narrower range within the operating range. Within this band the transducer is guaranteed to meet its published specifications. Changes in temperature affect the output of the transducer in two ways. They may cause the zero output to change and may also affect the full scale output. The transducer performance specification should list these temperature errors as: �x% of full scale/�C, �x% of reading/ �C, �x% of full scale over the entire compensated temperature range, or �x% of reading for the entire compensated temperature range. Not having these figures available will cause you uncertainty when using a transducer. Is the change in transducer output due to a change in pressure or a change in temperature? Honeywell's Data Instruments division specifies the operating and compensated ranges and the temperature coefficients of zero and span for every transducer it sells. The temperature effects on a transducer are often the most complicated part of understanding how to use a transducer.

What output signal should I use?
Nearly all transducers are available with either a millivolt, amplified voltage, milliampere, or frequency output. The output you select will depend on the distance between the transducer and your system's controller or display, the presence of "noise" or other electrical interference, whether amplification is necessary, and where it is best to place the amplifier. For many OEM products with a short distance between the transducer and the controller, millivolt output is usually adequate and less costly.

If you need to amplify a transducer's output, it may be easier to use a different transducer with a built-in amplifier. For long cable runs, or areas with high electrical noise, a milliampere or frequency output is desirable. For environments with very high levels of RFI or EMI, you will need to consider special shielding and filtering in addition to milliampere or frequency outputs.

What is excitation voltage?
The type of output desired may determine the excitation voltage you need. Many amplified transducers have built-in voltage regulators and will operate over a wide range of voltages from an unregulated power source. Some transducers are ratiometric and require a regulated excitation. The power available may dictate whether you use a regulated or unregulated transducer. Consider the trade-offs between the available excitation and system cost.

Do I need the transducer to be interchangeable?
Is it important that the transducers are interchangeable from system to system, or will you calibrate each unit as part of the system? This is important, especially for an OEM. Once you have shipped your product to your customer, the cost of field calibration can be very high. If the transducers are truly interchangeable, you should be able to replace a transducer in the field and expect the system to stay within specification.

How stable does the transducer need to be over time?
Most transducers will "drift" somewhat over time. It is important to discuss long term stability with the transducer vendor. This up front work can pay off in fewer field problems in the future.

How rugged does the transducer need to be?
One factor that is often overlooked, much to the chagrin of the user, is the ruggedness of the transducer, especially its housing. It is crucial to consider the transducer's prospective operating environment. Is it high in moisture or humidity? How will the transducer be installed? Will there be high levels of shock or vibration? All of these questions should be considered when selecting a housing style.

How will I connect the transducer to my electrical system?
Will a short cable on the transducer be adequate? Or, in the case of long cable runs, should I have a connector on the transducer? Most of Honeywell Data Instruments pressure transducers can be supplied with cable or optional connectors.

Choosing the transducer you need.

Review our products page to find which models meet your primary requirements. From there, you can refer to the details of these models on the product specification pages.