<3.Construction and Function>
3-14
IM 11R02A01-02E
5th Edition : Dec. 28, 2016-00
3.5.3
Correcting Computation
CM6G sets the differential pressure of both sample gas (∆Pg) and air (∆Pa) to 500 Pa. In order
to correct the indication error due to the variation of the differential pressure (Flow rate), the
correcting computation is practiced.
The detection signal is obtained through the measurement with the standard differential pressure
of 500 Pa, but if each differential pressure change to ∆Pg and ∆Pa (≠500 Pa), the detection
signal shall be changed from Eo to E’o.
E’o = Eo
(3.1)
•
∆
Pa
∆
Pg
Therefore, if you multiply the detection signal E’o by
∆
Pg
∆
Pa
/
, you can correct to the value
at the standard differential pressure.
In the computing program, each differential pressure is root-extracted and provides a differential
pressure correcting computation. The signal after the correction is range suppressed (ZERO)
and to further extended to SPAN. When it has a preheat circuit, deduct the amount of preheated
value and extend to SPAN, then being range suppressed and shall be extended again to
SPAN. Further as to generate the output of the calorific signal, the following density correction is
necessary:
K = C(WI)
(3.2)
•
ρ
g
Also it is necessary for each signal to operate with a timing matched with the signal of the calorific
detector and for this reason, dynamic characteristic function is provided. (A-CORR. RATE,
A-TIME, G-CORR. RATE, G-TIME)
Remarks: In case of pre-heating circuit exists, the formula is as follows:
∆θ = C
1
(3.3)
ρ
g
K
∆
Pa
∆
Pg
•
•
+ C
2
•
∆
Pa
H
H : Pre-heat calorie
C
1
, C
2
: Constant
ρg : Density of the gas
If the correction computation of the differential pressure is provided to ∆θ in the formula (6.3), it is
shown as per the following formula:
∆θ
(3.4)
•
•
+ C
2
•
∆
Pg
H
= C
1
∆
Pa
∆
Pg
ρ
g
K
The second clause of the right part in the formula (3.4) represent the preheat calorie, which, as
you can see in the formula (3.4), the matters concerning the preheating is varied according to the
change of differential pressure (∆Pg).
In this computing program, if there is preheating circuit, multiply the constant by the differential
pressure signal, and after correcting the differential pressure to the preheating, the deduction of
the preheat calorie is computed.
Содержание CM6G
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