Co Sensor Operation; Co Sensor Testing Results; Co Sensor Current Consumption Results - Renesas RL78/I1D User Manual

DETECT-IT RL78/I1D detector boards kit
Current measurement can be done at J1 and J2 jumpers, using an ampere meter.
The power consumption of each detector board is the sum of VDD current (measured at J1) and VDD_SENSOR current
(measured at J2).
So when you are doing current measurement, you should remove the jumper and place the ampere meter for doing your
measurement.
J1 and J2 should be then be in position for normal operation of the board with battery or with E1 connection (CN02
power). When measuring current at J1 for example, J2 jumper should always be in place, and vice versa.

CO Sensor Operation

9.2.1

CO Sensor Testing results

The CO sensor is working well and can achieve 100ppm +/-10ppm accuracy if sensor firmware is calibrated. It also
works well with the varying Power supply voltage of 2.7V to 3.5V. For the Figaro TGS5042 CO sensor units tested, all
of them were within a narrow range of output value, so only one CO Firmware threshold value was used, and it was
accurate enough for 100ppm +/-10ppm. However, if other TGS5042 sensors were used with much higher CO gas
sensor gain, the Firmware threshold (one single constant value) would need to be modified to accommodate it.
The existing Firmware threshold is good for ~1.3-1.4nA/PPM sensitivity. (TGS5042 spec range is 1.2nA-2.4nA/PPM).
To test the CO sensor for gas concentration accuracy we used a Kidde Carbon Monoxide Alarm, Model KN-COPP-B-
LPM, which has an LCD readout capable of showing CO gas concentration levels of 0-999ppm. For measurement
TM
setup, a Zip-Loc style bag was used to contain the CO sensor board, the Kidde CO alarm measuring unit and CO gas
itself. This way it is also possible to measure the DC output of trans-conductance amplifier output AMP0O and verify
that the alarm threshold is triggered at appropriate level. For the 1.425nA/ppm CO sensor example (calibration value is
written on the canister as explain below), and condition VDD = 3.3V, the AMP0O output should trigger the CO alarm
at approximately:
0.3V (VDD/11 bias) + 0.1295V = 0.4295V
9.2.2

CO Sensor Current Consumption results

The average current drain of the CO sensor board was measured at 8.5µA @ VDD = 2.7V to 10.6µA @VDD = 3.4V,
which is well under the target goal of 42.3µA average for 4 year battery life. CO Alarm ON state current is about
57.7mA @VDD= 2.7V and about 73.0mA @VDD = 3.4V. This current is primarily due to buzzer current, as the MCU
only draws ~1.3mA-2.0mA typical @8MHz, with the 2.0mA typical value occurring with both MCU and ADC active.
UM-YDETECT-IT-RL78 V1.30
Figure Measurement for Glass Break detector
Kit User Manual
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