DFA RTU Measurement Resolution
The DFA Remote Terminal Unit has an 8-bit or 10-bit data resolution for analog values and a 16-bit or 32-bit data resolution
for counter values. Counters may also be programmatically set to any data resolution within the range of 16-bit to 32-bit.
The data conversion of the analog input value depends on the RTU’s internal factors. Over the analog value’s measurement
range, the data conversion is as follows:
- 8-bit data resolution has 255 discrete values.
- 10-bit data resolution has 1024 discrete values.
- 12-bit data resolution has 4096 discrete values.
Example:
For an elevated tank with a bowl of 29 feet, the DFA RTU measures the tank’s water level with the following accuracy
for each data bit resolution over the measurement range.
- 8-bit data resolution = ± 1.4 inches (29 feet x 12 inches / 255 discrete values = 1.3647 inches)
- 10-bit data resolution = ± .34 inches (29 feet x 12 inches / 1024 discrete values = .3398 inches)
- 12-bit data resolution = ± .085 of an inch (29 feet x 12 inches / 4096 discrete values = .0849 inches)
In conclusion, for tank water level monitoring a 10-bit or 12-bit resolution provides too fine of a measure for the application.
The RTU would be tying up the radio channel by constantly transmitting every water ripple or wave in the tank as the water
level changes. Because of this, DFA uses an 8-bit conversion for the analog input value, water level. This measures the
tank’s water level to within ± 1.4 inches of the actual level in the 29 foot bowl. Also the tank’s RTU is generally set to
call into the SCC on every 3% change in the tank’s water level or every 10.44 inches change in water level.
|
|
|
