sca100t VTI Hamlin, sca100t Datasheet - Page 13

• Manufacturer Part Number: sca100t
• Description: The Sca100t Dual Axis Inclinometer Series
• Manufacturer: VTI Hamlin

2.6 Self Test and Failure Detection Modes
VTI Technologies Oy
www.vti.fi
As an example following table contains data register values and calculated differential digital
output values with -5, -1 0, 1 and 5 degree tilt angles.
To ensure reliable measurement results the SCA100T has continuous interconnection failure and
calibration memory validity detection. A detected failure forces the output signal close to power
supply ground or VDD level, outside the normal output range. The normal output ranges are:
analog 0.25-4.75 V (@Vdd=5V) and SPI 102...1945 counts.
The calibration memory validity is verified by continuously running parity check for the control
register memory content. In the case where a parity error is detected, the control register is
automatically re-loaded from the EEPROM. If a new parity error is detected after re-loading data
both analog output voltages are forced to go close to ground level (<0.25 V) and SPI outputs go
below 102 counts.
The SCA100T also includes a separate self test mode. The true self test simulates acceleration, or
deceleration, using an electrostatic force. The electrostatic force simulates acceleration that is high
enough to deflect the proof mass to the extreme positive position, and this causes the output signal
to go to the maximum value. The self test function is activated either by a separate on-off
command on the self test input, or through the SPI.
The self-test generates an electrostatic force, deflecting the sensing element’s proof mass, thus
checking the complete signal path. The true self test performs following checks:
The created deflection can be seen in both the SPI and analogue output.s The self test function is
activated digitally by a STX or STY command, and de-activated by a MEAS command. Self test
can be also activated applying logic”1” (positive supply voltage level) to ST pins (pins 9 & 10) of
SCA100T. The self test Input high voltage level is 4 – Vdd+0.3 V and input low voltage level is 0.3
– 1 V. The self test function must not be activated for both channels at the same time.
Angle
[°]
-5
-1
0
1
5
•
•
•
•
Sensing element movement check
ASIC signal path check
PCB signal path check
Micro controller A/D and signal path check
Acceleration
[mg]
-87.16
-17.45
0
17.45
87.16
RDAX (SCA100T-
D01)
dec: 881
bin: 011 0111 0001
dec: 995
bin: 011 1110 0011
dec: 1024
bin: 100 0000 0000
dec: 1053
bin: 100 0001 1101
dec: 1167
bin: 100 1000 1111
Subject to changes
Doc. nr. 8261800
RDAX (SCA100T-
D02)
dec: 953
bin: 011 1011 1001
dec: 1010
bin: 011 1111 0010
dec: 1024
bin: 100 0000 0000
dec: 1038
bin: 100 0000 1110
dec: 1095
bin: 100 0100 0111
SCA100T Series
Rev.A
13/18