L60iF Issue 9 November 2018
19
A1.1 Temperature compensation
The algorithm which generates the correction is
T is the measured temperature of the pump during operation
Tc is the cold temperature (taken at the start of calibration)
Th is the hot temperature (taken after pump has reached running temperature)
Lc is the L60iF reading when the pump is cold (Tc)
Lh is the L60iF reading when the pump is hot (Th)
Gc is the Flow gauge reading when the pump is cold (Tc)
Gh is the Flow Gauge reading when the pump is hot (Th)
For example,
if Tc = 13°C, Th = 44°C, Lc = 74.7, Lh = 66.2, Gc = 71 and Gh = 66.5 l/min
The general equation for correction under these circumstances is
At 44° there is no compensation, and at say, 20°C the compensation is
(20 - 44) / 7.75 = -3 litre/minute.
At 13°C, the compensation is (13 - 44) / 7.75 = -4 litre/minute.
This is what would be expected since at the beginning of the test, when the temperature was 13°C, the true
(Flow Gauge) reading was 71 l/min and the L60iF internal reading was 74.7l/min. The small error of 0.3l/min
is negligible, and is caused by the assumption that the error is linear with temperature change. The true
variation is slightly non-linear. However an error of 0.3 in 71 l/min represents an error of less than 0.4%.
The error falls linearly from -4 to 0 l/min as the temperature rises from 13 to 44°C.
The benefit of this correction is that the readings on the L60iF are correct from power up.
Gh
Gc
Lh
Lc
Tc
Th
Th
T
u
»¼
º
«¬
ª
75
.
7
44
4
31
44
5
.
66
71
2
.
66
7
.
74
13
44
44
u
u
»¼
º
«¬
ª
T
T
T