Dwyer DPM - Manual (Page 26)

Particulate Monitoring Systems
Installation & Operating Manual
Document No. 210-1003-M Page 19 ©2007
4-20mA Logarithmic Output
To convert the 4-20mA logarithmic output back to pA, use the following formula:
1. Compute the number of output decades:
Number_Of_Decades =Log [(4-20mA Output Span)/(4-20mA Minimum_Scale)]
2. Scale mA input to proper log(10) argument:
Y = Number_Of_Decades * (mA – 4.00) / 16
3. Convert log(10) argument to pA:
pA = 10^(Y) * (4-20mA Minimum_Scale)
Example #1: See Menu #2 for details.
Where: 4-20mA Minimum Scale = 0.1pA
4-20mA Output Span = 1000pA
Number_Of_Decades = Log (1000 / 0.1) = 4
4-20mA Output Y pA
4 0 0.1
5 0.25 0.2
6 0.5 0.3
7 0.75 0.6
8 1 1.0
9 1.25 1.8
10 1.5 3.2
11 1.75 5.6
12 2 10.0
13 2.25 17.8
14 2.5 31.6
15 2.75 56.2
16 3 100.0
17 3.25 177.8
18 3.5 316.2
19 3.75 562.3
20 4 1000.0