FIC98648 Datasheet, PDF (6/14 Pages) List of Unclassifed Manufacturers – Microprocessor for use with TGS4160 in automatic CO2 monitors

TECHNICAL INFORMATION FOR FIC98648
concentration readings. The pulse width against a
cycle corresponds to the CO2 concentration as shown
in Figure 2. This pulse width is then converted to an
analog output voltage between 0 ~ 3V by the circuit
(please refer to Sec. 5-4 - CO2 concentration circuit).
4-6-2 Damper control signal output (Pin No. 16)
The output from port R60 is set to “H” under normal
conditions in a clean environment, indicating that the
damper should be closed. When a CO2 reading
exceeds the preset level of the Open Damper
Threshold (Cd1) as shown in Table 2, an “L” signal is
output from port R60 as a signal for opening the
damper. When CO2 drops below the preset level of
the Close Damper Threshold (Cd2), the output from
port R60 returns to an “H” signal for closing a
damper. “H” is also output from port R60 during
initial warm-up time and whenever a malfunction
signal is output.
4-7 LED display signal output (Pin Nos. 18 & 19)
The following LED display signals are output from
port R62 (red LED) and port R63 (green LED):
4-7-1 Initial warm-up time
During the initial warm-up period (see Sec. 4-1-1),
an alternating H/L signal is output from port R63
every 0.5 seconds, causing the green LED to alternate
between on and off every 0.5 seconds. “L” is output
continuously from R62 during this period.
4-7-2 Normal operation mode
When the CO2 concentration is lower than the preset
threshold level for the damper control (Cd1), “L” is
output from port R62 and “H” is output from the
R63, causing the green LED to be lit continuously.
Conversely, if the CO2 concentration is higher than
the preset threshold level for the damper control
(Cd1), “H” is output from port R62 and “L” is output
from port R63, causing the red LED to be lit
continuously.
4-7-3 Malfunction mode
When a malfunction has been detected (see Sec. 4-8),
an alternating H/L signal is output from port R62
every 0.5 seconds, causing the red LED to alternate
between on and off every 0.5 seconds. “L” is output
continuously from R63 during this period.
H
L
A
B
C
Approx. 65 msec.
A: [(CO2 concentration) / 3000] x C
B: C - [(CO2 concentration) / 3000] x C
C: approx. 65msec.
Figure 2 - PWM signal for CO2 concentration
4-8 Malfunction signal output (Pin No. 17)
An “H” signal is output from port R61 under normal
operation conditions. When a malfunction is detected on
the gas sensor’s heater and/or the benchmark level Vg,
an “L” signal is output from port R61. The following
conditions would generate a malfunction signal:
(a) Sensor heater breakage—when the thermistor’s
signal (VT) remains at a level equivalent to 50°C
or lower for over 10 seconds, the heater can be
considered to have malfunctioned. Monitoring of
this condition commences 30 minutes after
powering on.
(b) Benchmark level Vg malfunction—when the
benchmark level Vg (gas sensor’s signal) cannot
be adjusted in the range between 25 and 51 counts
at AD converted value within 10 minutes after
the adjustment is started, a malfunction is
considered to have occurred.
The relationship between signal output ports and
their output signals under malfunction mode can be
seen in Table 6.
Terminal
Signal
Indication
CO2 concentration
signal (R91)
“L” signal
0ppm
Damper control
signal (R60)
“H” signal
Close
Red LED (R62)
Alternate H/L signal
(0.5 sec./0.5 sec.)
On/Off
Green LED (R63)
“L” signal
Off
Bias signal (R90) Hold the level
Off
Table 6 - Malfunction signal
4-9 Benchmark renewal status signal output (Pin No. 26)
When the benchmark level has been renewed, an “L”
signal is output from port R92 for one second to
indicate the status. An “H” signal is normally output
from this port.
Revised 08/03
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