The following step-by-step guide will walk you through the basics of selecting a gauge, once you have determined the type of gauge you need, use the Gauge Finder to find and purchase gauge.
If you have a special application, need a unique gauge, or just need more information, give us a call at 844-358-3099.
Choose from Low, Specialty, Standard, Vacuum and Compound Pressure Ranges.
The first thing you need to know when purchasing a pressure gauge is what pressure range (pounds per square inch, or “psi” is standard) you need. Since the accuracy of most pressure gauges is best in the middle third of a gauge, you should always select a gauge with a range that is about twice your normal operating pressure. For example, if you have an air compressor with a normal working pressure of 50 psi you want to select a gauge with a 100 psi range.
The rule of thumb with pressure gauges is that when the operating pressure of the system is normal, the needle should be pointing straight up or in the “twelve o’clock” position. This makes the gauge easier to read at a glance – if the pointer is straight up, things are normal. Gauges are most accurate in the middle third of their range, so you’ll also get a better measurement at your most typical pressure.
If you cannot find a gauge at exactly twice your working pressure, go to the next step up. For example, if you want a 160 psi gauge and it is not in stock, a 200-psi gauge can be substituted. If the range is too low and the gauge is over-pressurized it will break. You want some room to spare at the top of the scale so that if your pressure goes above normal, it won’t damage the gauge.
The dial size refers to the diameter of the circular face of the gauge. The easiest way to choose a size is to measure the diameter of your old gauge. Our gauges range in dial sizes from 1-inch for tight spaces to 10-inches for reading from a distance. When selecting a gauge choose one that fits within the physical space available and a gauge size that is easy to read where you have it installed.
If dial size is not important to you we recommend selecting a 2-1/2" gauge. If there is such a thing as a "standard" gauge size, this is it. The 2-1/2" gauge is by far the most common gauge that we sell and you will find hundreds of in-stock options to choose from. View the dimensional drawings if you need more information. Dimensional drawings for all of our gauges are found on every product page and provide the exact measurements.
You also have to consider connection size. For 2-1/2" dial sizes, a 1/4-inch NPT (National Pipe Thread) is by far the most common size. If you're replacing a gauge, you want to be aware of the existing connection size. Other common connection sizes are 1/8-inch NPT (for 1-1/2" & 2" dials) and 1/2 inch NPT (for 4" and greater dial sizes).
There are two basic connection types for mounting: back and lower. The back mount is what it sounds like. The connection protrudes from the back of the gauge. In a lower-mount (sometimes called a stem mount), the connection is on the bottom of the gauge. Which type you need will usually be pretty obvious. Manufacturers divide back mounts into "center back" and "lower back," (right in the middle of the back vs. down toward six-o'clock), but unless you're trying to fit the gauge into a tight space, or mount it in a panel, the difference usually doesn’t matter.
Accuracy span is the single factor that has the most influence on price, so you want to get a gauge that is accurate enough – but not more accurate than you need. Gauges are available with accuracies from +/-3/2/3% to 0.25% of span (ASME grade B to grade 3A). Consider your application to determine accuracy needs. If the gauge is for your backyard pool, you don’t need a lot of accuracy and a "3-2-3" gauge should be just fine. These gauges are accurate to plus or minus 3% in the bottom third and top third of their range, and within 2% in the middle third. If you need something a bit better than that, a gauge with 1.5% accuracy good choice for applications where small differences in pressure aren’t critical. Gauges with 1.5% accuracy will give you a more accurate reading (+/-1.5% across the range) than a 3-2-3, but are still quite affordable.
If you really do need to keep track of whether your system is at 59 PSI or 59.5 psi, you need a higher accuracy gauge, and we carry them, all the way up to a level of 0.25%. If you have an application where accuracy is that critical, you probably know it. If you aren’t sure, give us a call and we’ll make sure you get the right gauge.
There are two reasons to fill a gauge with liquid (we generally use glycerine). Liquid steadies the pointer and makes the gauge easier to read. The liquid also lubricates the internal parts of the gauge, making it last longer. So if you have an application with a lot of vibration, or want to get a longer life out of your gauge, go for a liquid-filled case. We have three options available: dry case, glycerine filled and dry case-liquid fillable. "Dry case" gauges are not able to be filled with liquid. "Glycerine-filled" gauges are shipped filled with liquid. "Dry-case, Liquid Fillable" gauges are for customers who prefer to fill their own gauges.
Glycerine is the most common all-purpose liquid to use. If you need to use a gauge in extreme temperature conditions, either very low (below -20F/-29C) or very high (over 180F/82C), call us for other options.
The "wetted parts" of the gauge are the parts that come in contact with the process that is being measured (liquid, air, gas, etc). We have special materials for unusual applications (for example, highly corrosive liquids) but by far the most common materials are brass and stainless steel. Brass is less expensive, and is a great choice with non-corrosive gases or liquids (for example: air, water, or gasoline). Stainless steel stands up better to acid and alkaline substances and is more durable.