How to Calibrate a Pressure Gauge

This article will discuss the basic principles of calibrating a pressure gauge, as well as some basic explanations of what a pressure gauge is and why it is important to frequently calibrate this important instrument.

What is a Pressure Gauge?

Very simply, a pressure gauge is an instrument used to measure the pressure of either a liquid or a gas that is held in a contained atmosphere – i.e. a tank.

It does this by calculating the at rest force of the contained gas or liquid and comparing it to the atmosphere that the tank is found in. The measurement will be given in Pounds per Square Inch (PSI) or Newtons Per Square Inch.

Why Calibrate Pressure Gauges?

For one thing, the essential operation of machinery or industrial functions is often dependent upon accurate readings of all sorts of scales, balances and gauges. Gauges to measure pressure are one of the most frequently encountered instruments in a wide variety of industrial settings. This highlights the importance of this instrument within industrial and commercial properties.

In addition, there is also often an element of safety to ensuring that these instruments are frequently and accurately calibrated. High pressure after all can damage equipment and even pose a serious health and safety risk to staff operating the machinery. Accurately calibrated gauges help to effectively monitor pressure, helping to ensure a safe working environment for all.

How to Calibrate a Pressure Gauge

The first thing to note is that there is no universal way to calibrate every single pressure gauge – there are simply too many types out there!

This then is a general rule of thumb of the process, highlighting some of the more important stages of the calibration process.

If you are unsure, it is always a good idea to consult a professional calibration service for advice, such as Calibration Lab.

  1. The very first stage is to establish that the “Standard” to be used has itself been calibrated to its manufactures instructions. The standard is the benchmark against which your gauge will be calibrated, so it must be accurately calibrated itself!
  2. Using a block valve, connect the pressure gauge to the pressure source. The block valve will isolate this source from the main body of liquid or gas that is held under pressure.  A bleeding valve must also be used release the pressure.
  3. Next, ensure that indicator has been set to zero. This is the position it must be in before calibration begins.
  4. Increase the pressure to the valve until it receives the maximum permissible pressure for the gauge being calibrated. Adjust the gauge so it reflects that maximum pressure has been applied.
  5.  Next it is time to isolate the source of the pressure. Once this has been done, use the bleed valve to ensure the system is completely depressurized.
  6. After this complete depressurization, you must now check that the indicator on the valve has returned to zero. Again, and just as in step 4, adjust the gauge if required so that the indicator valve shows the correct reading – in this instance zero.
  7. Repeat steps 4 through to 6 until the gauge gives correct readings without any adjustments being required.
  8. It is worth pressurizing the gauge to 50% as well and ensuring that the gauge indicator also gives an accurate reading at this point too. It is an additional step that is not truly necessary for a calibration, but can help to make the process even more accurate.
  9. Remove the “Standard” gauge, block and bleeding valves.

Congratulations – you have now calibrated your pressure gauge! Of course, as we mentioned above, professional calibration services are out there to offer advice and assistance – and even to calibrate your gauges if you prefer to bring in a professional.

How to Calibrate a Temperature Transmitter

Within many factories and industrial plants, Temperature Transmitters are becoming increasingly popular instruments.

Just as with any other measuring instruments, it is important that they are regularly calibrated so that they can perform their functions and provide accurate readings. In this article, we will discuss how that calibration process can be achieved.

But before we get there, let us just discuss –

What is a Temperature Transmitter?

To ensure that this article will discuss the calibration of the types of instruments you are dealing with, let us briefly clarify what a temperature transmitter is.

Temperature Transmitters work in to assist in the monitoring of temperature in a remote process. They convert temperature readings to a signal that can be transmitted to a range of instruments that convert the signal to data that can be read and recorded.

Because of the nature both of their operation and the fact that they essentially transmit date, it is important they are correctly calibrated to they are as accurate as possible.

How to Calibrate a Temperature Transmitter

So now we know what we are talking about, and why it’s important to calibrate it, the next stage is to discuss the calibration process itself!

We should note at this stage that there is not a universal method that will cover the calibration of all Temperature Transmitter devices. There are quite simply too many devices from different manufactures on the market to make that claim.

Instead we will discuss a more general-purpose guide that cover the basics of the calibration process for this instrument. If in doubt, it is highly recommended that you refer to the original instructions of your transmitter, that you contact the original manufacturer for advice and guidance or that your consult a professional calibration company.

Equipment

So just as with any other process, the first thing to do of course is to gather all of the equipment and materials that will be required for the job.

As we discussed above, this equipment list could alter slightly depending on the specifics of your own transmitter.  As a general rule of thumb however you will require:

  •         A digital Voltmeter rated to 1mv. This is the key piece of equipment in the calibration process so it should be a model with as high a degree of accuracy as you can find.
  •         A power source, of a voltage of the same level used to power the transmitter.
  •         A Resistance Decade Box. Again, this should be a model with the highest precision you can find.
  •         You will need to remove the housing cover on the transmitters, so you will also need suitable tools for his, i.e. screwdrivers or wrenches.

Method

  1. The first step is to disconnect power, and then to remove the housing cover from the transmitter so that you can gain access to the transmitter terminal itself.
  2. If the transmitter has recently been operational, the RTD (Resistance Temperature Detector) may still be connected. If this is the case, disconnect it now, including all lead connections.
  3. Make sure that the RTD resistance is set to the required level (i.e. 0 Celsius)
  4. Turn the power supply on.
  5. On the Resistance Decade Box, set a resistance that corresponds to the required base temperature, adjusting the potentiometer on the transmitter itself until output is reading a steady 4mA.
  6. Repeat step 5 expect this time you are setting the decade box to the resistance that corresponds with the full temperature instead of the base. Again, adjust the potentiometer on the transmitter until it reads 20mA in this instance.
  7. Repeat steps 5 & 6 until readings of 4 and 20mA are achieved at each respective temperature with no adjustment.
  8. Remove all tools, replace transmitter cover and secure into position.

Congratulations, you have calibrated your Temperature Transmitter!

Why is the Calibration Process Important?

Accurate measurements are more important than ever in today’s high tech world. In industrial, commercial and retail sectors – to name just a few – scale and balances ensure that goods are manufactured and sold correctly.

Within industrial plants, various gauges and measuring devices are in place to ensure that all processes are completed effectively and safely.

Even at home or in our personal lives, we rely on numerous pieces of tech to tell us measurements – everything from how much electricity we are using to the speed our cars are travelling at.

At work, at home and at play devices designed to give us measurements surround us and provide a constant stream of data, readings and information.

But what if they are not accurate?

To avoid this, it is essential that a programme of thorough and regular calibration is completed. In fact, providing accurate measurements is possibly one of the key benefits that calibration can bring – but it is certainly not the only benefit you can achieve.

In addition to accurate measurements, there are three equally important benefits that are:

Safety

Many of the instruments and gauges we employ in everyday life are used to monitor processes and quantities such as electric current, heat and pressure.

Where staff interact with the machinery that is creating or using these things, it is essential for their safety that the measurements they rely on are accurate. False readings can cause machinery to fail; it can override safety parameters and can create a dangerous working atmosphere.

False readings from devices can have serious safety implications across a range of sectors too. Within hospitality for example, food can be stored at incorrect temperatures or not cooked to sufficient temperatures to remove all traces of bacteria.

This is just one example of course, but across all industrial, commercial and retail sectors there will be numerous examples of how a poorly calibrated device can give false or inaccurate readings that can put people’s safety at serious risk.

Cost Reduction

Some companies will avoid regular calibration of their instruments as they see it as an unnecessary additional cost. The sad thing for them (and the good news for savvier companies, who appreciate the opposite) is that they don’t see this small saving as a false economy.

The truth is that instruments that have not been calibrated properly will give false or incorrect readings that can have serious implications on the manufacturing process within an industrial plant. This can lead to errors in production that can cause entire lines to be written off as undeliverable.

This isn’t restricted to the manufacturing sector either. In retail, for example, poorly calibrated scales and balances could be leading to the sale of more product than is being paid for – all just because it can’t be measured accurately!

Certification Maintenance

By calibrating your instruments with a calibration service, you will receive from them certification that the calibration has been completed to a professional level.

This can be useful to you for two reasons.

One, it allows you to include the fact your instruments are calibrated within any promotional material that you produce. The fact that you care about accuracy can be a big selling point for your or your company, and show potential customers that you’re a professional body with high standards.

It can also help when getting insurance, especially by showing that your property and machinery are both well maintained and fit for purpose.

So now you can see the benefits of calibration, hopefully you will consider implementing a regular programme of it as part of your maintenance.