Pressure Measurement, Utility
Understanding Digital Displays
Digital display specifications can be confusing. Here is a short application note that describes the terminology and capabilities of a digital display.
Digital displays are specified as being either 3-1/2 digits or 4-1/2 digits. In a 3-1/2 digit display the three rightmost digits may read any value between 1 and 9. The left-most digit is limited to 1 or a blank. It is often easier to think in terms of counts: a 3-1/2 digit display can read up to 1999 counts, so it is suitable for displaying readings that have a maximum value of 20, 200 or 2000. Note that the decimal point may be placed within the right most three digits: 19.99, 199.9 or 1999.
Similarly a 4-1/2 digit display may read 19.999, 199.99, 1999.9 or 19999.
To specify the correct number of digits in a display, keep the following in mind: The resolution of the display should be five to twenty times better than the accuracy.
For example, if a 20 psi transducer with 0.25% FS accuracy is used, a 3-1/2 digit display configured to read 19.99 psi will provide a resolution of 0.01 psi when the accuracy of the transducer is 0.05 psi, and this is a good balance between resolution of the display and accuracy of the sensor.
A 4-1/2 digit display specified for the same transducer would read 19.999 psig at full scale, and the last digit would be unusable since it represents 50 times more resolution than the transducer accuracy.
However, if the transducer accuracy is 0.1% FS, then the 4-1/2 digit display would be appropriate because the accuracy of the transducer is now 0.02 psi and the 4-1/2 digit display would have a resolution 20 times greater than the accuracy. A 3-1/2 digit display, by contrast, would only read to 0.01 psi – just twice the accuracy of the sensor.
The diagram above shows how the 3-1/2 and 4-1/2 digital displays are used.
Check out Validyne products with a Digital Display
PS309 Portable Digital Manometer
PS409 Digital Panel Mount Manometer
P532 Ultra-Low Pressure Transmitter
Related posts
Utility
Nuclear Qualified Draft Range Differential Pressure Transmitter
The N-DR800 is a nuclear qualified draft range differential pressure transmitter designed for use in Nuclear power plants for very low pressure measurements such as HEPA vent filter, HEPA filter…
Oil & Gas, Pressure Measurement, Utility
Pressure Transmitter to Detect Burner Flame Instability
Large-scale industrial installations such as refineries and chemical plants often have large direct-fired heaters that are used in the processing of fluids and gases. Such heaters must now be designed…
Construction, Data Acquisition, Design, Military, Utility
Static Load Structural Testing
Structures that must bear weight or force are tested after construction by applying a static load and measuring the deflection of the structural elements. The deflections must be within permissible…
Data Acquisition, Utility
Elevated Highway Column Testing
Elevated highways are common in new road construction. The road bed is raised above the land surface by columns, or piers, set deep in the ground. This is advantageous in…
Pressure Measurement
Leak Test using Pressure Transducers
Introduction: Leak tests are often performed on manufactured items before shipment to verify pressure integrity. The most common way of doing this is to pressurize the article, seal it off…Comments are closed
