In-Situ Aqua TROLL 400 Modbus and SDI-12 Reference Guide - Manual (Page 53)

Register Size
(registers)
Mode & Access Level
(R/W)
Data
Type
Description
1641 2 R1/W3 float
Slope, m
2
in pH/mV
(default = -0.016903313)
1643 2 R1/W3 float Offset, b
2
in pH (default = 7.0)
1645 1 R1/W3 ushort ORP solution type (default = 0)
1646 2 R1/W3 float mV value of solution (default = 0)
1648 2 R1/W3 float mV response in solution (default = 0)
1650 2 R1/W3 float
Temperature of solution, T
orp
in °C
(default = 25)
1652 2 R1/W3 float Slope, m
orp
in mV/mV (default = 1.0)
1654 2 R1/W3 float
Offset, b
orp
in mV
(default = 0.0, limit = +/-1000)
7.3.1 pH Measured Value
The measured value is derived from either one line segment (created from a one-point or two-
point calibration) or two line segments (created from a three-point calibration).
For one line segment:
pH = (T
1K
/ T
K
) × m1 × mV + b
1
For two line segments:
mV > mV2: pH = (T
1K
/ T
K
) × m
1
× mV + b
1
mV <= mV
2
: pH = (T
2K
/ T
K
) × m
2
× mV + b
2
Where:
mV is the measured sensor millivolts
T
K
is the measured temperature in °K
T
1K
is the calibration temperature converted to °K. (T
1K
= T
1
+ 273.15)
T
2K
is the calibration temperature converted to °K. (T
2K
= T
2
+ 273.15)
m
1
and b
1
are slope and offset for segment one respectively
m
2
and b
2
are slope and offset for segment two respectively
pH is the calculated result
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