How to Specify a Digital Pressure Gauge ~ Learning Instrumentation And Control Engineering Learning Instrumentation And Control Engineering

How to Specify a Digital Pressure Gauge

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Digital Pressure Gauge (Photo Credit: ASHCROFT)
With the advancement in gauge technology, digital pressure gauges are becoming more popular. With their  superior accuracy and functionality, most new plants are increasingly employing digital gauges especially in industrial processes where accuracy is paramount.

Although we probably all know the key parameters required to purchase a regular dial gauge, we may be at a loss when it comes to digital gauges. This is because in addition to the regular features of a typical pressure gauge, digital gauges are equipped with other functionalities that need to be specified. 

Digital pressure gauges are specified in much the same way a typical pressure gauge will be specified except for few specification items that are specific to digital pressure gauges. The table below shows the key parameters that must be taken into consideration for a general purpose digital pressure gauge to be accurately specified.
Parameters to Specify
Details of Specification
AccuracyTypical accuracies include ±0.1% FS, ±0.25% FS, ±0.5% FS etc 
Case Size  Standard case sizes include 3’’, 41/2’’,6’’ etc. 
Case MaterialDepending on your application, typical ones include 300 series stainless steel, fiberglass reinforced thermoplastic, black painted aluminium etc
Wetted Materials Specify materials that will resist corrosion. Typical materials include 17 – 4 PH stainless steel sensor, stainless steel socket etc
Socket Size Typical socket sizes include 1/8’’ , ¼’’ , ½’’ etc. 
Connection Specify whether process connection will be lower (6 o’clock), top or side
Measuring Range Specify the measuring range of gauge in the desired unit. For example 15 psi through 20,000 psi, 0 – 100 bar etc
Power Source For digital pressure gauges, they could be powered through:
1. Alkaline batteries (two pieces of size AA typically)
2. C Alkaline batteries (two pieces)
3. Loop powered by a 4 – 20mA source
4. Line powered (specify voltage and current)
Specify the desired power source you desire for the digital gauge
Battery Life Battery life is specified in hours. Typical battery life include 500hrs, 1000hrs, 2000hrs etc
Battery Indicator Specify the battery indicator levels
Cycle Life Specify the cyle life of the digital pressure gauge. e.g 5million cycles, 10 million cycles etc
Operating Temperature Operating temperature of gauge is critical for accurate performance. Specify the operating temperature of gauge depending on temperature regime of the environment where the gauge is to be used.
Storage Temperature  Specify storage temperature of gauge
LCD Display Specify the type of LCD display
Character Height Specify the character height of the LCD display - specify height of upper character and that of lower character
Engineering Units Specify the engineering units you want your digital gauge to display - psi, bar, mmHg etc
Backlight Specify whether the LCD display should have a backlight especially in applications where illumination could be a problem especially at night
Enclosure Rating Specify the enclosure rating. Common enclosure rating for gauges is IP 67
Keypad Functions Specify the keypad functions of the gauge. Three key with multi press functionality are typical.