Digital pressure gauges offer highly accurate readings, rugged durability, and several advanced features which dial gauges cannot compete with. Today, we will look at two of the more popular features that allow your digital gauge to tell you more than just the current pressure: Peak Hold and Tare.
What is Peak Hold?
Peak Hold does exactly what its name says it should: maintains the highest reading on the digital display. The instrument is still taking accurate measurements, but only the peak reading is being displayed on the digital read-out. If your gauge has analog output, that output will continue to reflect the real-time pressure reading of the gauge. Only the digital display is affected by the Peak Hold setting.
What is Tare?
Tare is close what it sounds like, but with a different purpose in mind. In chemistry, we weigh empty containers prior to weighing actual substances so that we can adjust—tare—the scale to account for the weight of the container, giving us a more precise measurement of the substance in question.
For digital pressure gauges, the idea is similar. The Tare function sets a new 0 point (at the current reading), providing a baseline for measuring relative pressure. In contrast to Peak Hold, Tare does affect the analog output. When you set the new 0 point for relative pressure measurement at the gauge, the analog output adjusts to that new 0 point.
Both of these functions affect the digital display of your gauge. This is especially important to remember with Tare, as the digital display can show 0, or even negative pressure, while the gauge is still pressurized. So, for both Peak Hold and Tare, an icon will show on the display indicating which function is controlling the digital read-out. Make sure you disable both functions before removing a gauge from service.
Why use them?
What, then, is the value of these functions? What makes them worth the price of admission, so to speak? Let’s take a look.
Peak Hold allows the crew to monitor the peak pressure seen by a gauge quickly and visually. Yes, most gauges that have Peak Hold functions also have Min/Max functions; but those values are generally only available by navigating through menus, and, even then, can only be scrolled or cycled through. Min/Max cannot usually be set to constantly display on the digital readout.
The entire purpose of Peak Hold, on the other hand, is to maintain that peak value on the display. As long as Peak Hold is enabled, the value can be read without pushing buttons, toggling menu operations, or any other kind of hassle. Simply walk by, look at the gauge, and keep walking. It’s the easiest way to monitor the peak pressure seen by the gauge.
Use Tare to monitor change, or relative pressure. Let’s say you have a 100 psi gauge, but the base line pressure of your system is 35 psi. You can’t simply re-zero your gauge to 35 psi because 35 is beyond the 5%-of-full-scale limit for zeroing. However, by setting the Tare at 35 psi, you can measure net added pressure in your system.
So, with Tare set at 35 psi, if your gauge reads 17 psi, the actual pressure in the system is 52 psi. The same is true for the analog output of your gauge: with the Tare set at 35 psi, a system pressure of 52 psi will be interpreted as a reading of 17 psi.
Tare is also common when taking force or weight measurements. In order to do it right, you have to tare out the existing system load before you apply the desired weight or force. You can measure this in lbs or tones, or anything else really by entering custom multipliers into your gauge.
There are two inherent dangers with the Tare function, one that the gauge automatically protects against, and one that the gauge only helps to prevent. The first is overpressure. A 100 psi gauge tared to 35 psi will still reach full-scale at 100 psi, even though the reading will only show 65 psi. If the gauge reaches full-scale pressure, it will automatically turn off the Tare function in order to help prevent overpressure in the system and across the gauge.
The second danger is removing the gauge while it is still pressurized by the system. A gauge tared at 35 psi will show 0 psi even though 35 psi is present in the system. Always check the display for the T5 icon indicating that the Tare function is activated before removing the gauge from the system.
Both features are distinct and quite useful in the proper circumstances. They enable you to do more with your pressure gauge than you ever could with a dial. Contact us with any questions and we’ll help you find the right gauge feature for your application.
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