Sens SG-A1, User Manual

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SENS.413347.015RE
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8.3.5.3 Supply power to checking circuit. Within approximately 60 s after supply of
power voltage gas detector remains in self-test mode. At the same time on the front panel of
instrument there should be interrupted synchronous glowing of all indicators (glowing and
pause durations are approximately equal to 1 s).
Err is displayed on display of signaling
device MS-K-500-3 during this time, current in the 4...20 mA interface circuit is equal to
3.5±0.2 mA, Modbus holding register with 0 address is set to zero (see table 8.7), data
transmitted over HART: primary variable (Concentration, % LFL) is equal to 0xFFFFFFFF
(value of primary variable is equal to "NAN" in "Configuration of HART Gas Detectors" PC
program); secondary variable (value of current in line 4...20 mA) is equal to 3,5 mA.
Note - Current in 4...20 mA interface circuit, depending on indications of voltmeter
connected in parallel to measuring resistance coil, is calculated using formula shown in notes
below.
After self-test procedure, in case of failures absence and positive results of test, gas
detector is switched to measurement mode.
At the same time, indicators on face panel must be in the following state:
"THRESHOLD" - no glow;
"FAILURE" - no glow;
"POWER" - constant glow;
- indicator "% LFL% displays concentration value (only gas detector models with built-in
digital indicator).
After stabilization, indications read using all available interfaces, must be within
inaccuracy range determined by specifications of gas detector.
Note - Nominal static function of gas detector conversion using DC output signal I, mA, is
as follows:
I = I
N
+ K
n
• (C
D
- C
N
),
where: I
N
- lower threshold of DC output signal range, equal to 4 mA;
C
D
- actual value of verification component concentration in % LFL;
C
N
- lower limit of measurement range equal to 0% LFL;
K
n
- nominal coefficient of conversion mA/% LFL, calculated using formula:
N V
N V
п
C C
I I
K



where: I
V
, I
N
- upper and lower thresholds of DC output signal range, equal to 20 mA and 4
mA respectively;
С
V
, С
N
- upper and lower limits of measurement range equal to 100% LFL and 0% LFL
respectively.
Indications of gas detector via analogue current output (C, % LFL) are determined in
accordance with diagram shown in figure 8.1, as per formula:
н
n ks
ks izm ks
C
К
R
U U
C




0 .
where: K
n
- nominal coefficient of conversion mA/% LFL;
U
KS.IZM
- voltage drop measure on the measurement resistance coil, mV;
U
KS0
- voltage drop at measurement resistant coil corresponding to current I
N
and equal
to 400 mV;
R
KS
- nominal resistance of measurement resistance coil equal to 100 Ohm.
8.3.5.4 Perform checking of operational capability for relay 1 and relay 2 in accordance
with 8.5.3.3. To control state of relay contacts, use ohmmeter 1 and ohmmeter 2.
8.3.5.5 It is recommended to check zero calibration and sensitivity of gas detector in
accordance with 8.5.3.4 and 8.5.3.5.