Thursday, April 7, 2011

Digital Gauges

Digital gauges are becoming more common. The first company to offer digital manifold gauges was Digicool. When the first Digicool gauge sets came out, only the air conditioning techno-geeks and tool hounds had them. It will still be a few years before most mechanics use digital gauges, but many companies that traditionally make gauge manifold sets now have a digital offering. The list includes companies like JB, Refco, Robinair, and Yellow Jacket. Even companies who do not traditionally sell gauge manifolds offer digital manifold sets, including Field Piece and Testo. Many of these are billed as digital system analyzers because they do more than read pressure. They also show saturation temperature and have a place to plug in a thermocouple temperature probe for reading line temperatures, providing all the information necessary to determine system superheat and subcooling. Many will calculate the system superheat and subcooling and display them in real time. Some will even suggest what the target system superheat and subcooling should be based on the system operating conditions. There are several digital analyzers available that will also read vacuum in microns, doubling as a deep vacuum gauge.  The strongest argument for digital gauges is accuracy. They are more accurate than the best bourdon tube gauges can hope to be. Accuracy is becoming increasingly important as system operating efficiency becomes more important. 

The prices are coming down, but you will still pay a premium for a digital set over a good quality analog set. If you decide to take the plunge here are a few things to consider. When comparing the cost of a digital gauge set that reads deep vacuum, remember that a vacuum gauge alone can easily cost $200. Also remember that you are buying a manifold, not just a set of gauges. So sets that come on better manifolds cost more, just like analog gauge sets. One caveat when shopping - there are some very inexpensive digital gauge manifolds advertised on line that are intended specifically for cars and 134a. They will NOT work on systems which use other types of refrigerant, especially not R410a! These days you really should not consider investing in a high tech tool that will not work with R410a.

 However, in the next few years I expect the same type of technology/price inversion that we have seen with electric multimeters where the older technology actually costs more than the newer technology. When Fluke digital meters were first being used in HVACR, they typically were more expensive than their analog counterparts of comparable quality. Now, a Simpson 260 analog VOM costs more than a Fluke 116 multimeter, and the Simpson is less resistant to field abuse and really less useful for the HVACR technician in general. The older technology electric meter technology is actually more expensive than the newer digital meters. I realize the analogy is imperfect: a Simpson 260 analog VOM is considerably more complex than a bourdon tube gauge.  However, I expect digital gauge sets  to be in the same price range as good quality analog bourdon tube gauge sets within 5 years.



  1. Digital Manifolds are certainly the way forward. The new Testo 550 digital manifold provides high performance at an affordable price. The instrument's intuitive operation allows you to measure high and low pressure quickly and precisely, and with the two temperature inputs you can simultaneously calculate superheating and subcooling. The brightly illuminated display allows fast and easy readout of all measurement values and there are 31 refrigerants stored in the instrument, which can be selected via a direct button. Nice.

    Look forward to seeing more from Testo.


  2. Is spamming part of Testo's internet marketing strategy? The above comment links to Testo's homepage, but pretends it is from a user. This is actually an illegal thing to do: its called "astroturfing"