Datasheet

MAX31865
RTD-to-Digital Converter
21Maxim Integrated
Table 10. Decoding RTD Faults for 2-Wire Setups When Fault Bit in RTD Data LSB
Register = 1
Table 11. Decoding RTD Faults for 3-Wire Setups When Fault Bit in RTD Data LSB
Register = 1
FAULT
STATUS
BIT SET
DESCRIPTION OF POSSIBLE
CAUSE
CONDITION DETECTED
DESCRIPTION OF
RESULTING DATA
D7 Open RTD element
Measured resistance greater than High Fault
Threshold value
Full scale
D6
Shorted RTD element
Measured resistance less than Low Fault
Threshold value
Near zero
RTDIN+ shorted low
D5
Open RTD
V
REFIN-
> 0.85 x V
BIAS
Full scale
RTDIN+ shorted high Indeterminate
RTDIN- shorted high Indeterminate
D4 RTDIN- shorted low V
REFIN-
< 0.85 x V
BIAS
(FORCE- open) Appear to be valid
D3
RTDIN- shorted low
V
RTDIN-
< 0.85 x V
BIAS
(FORCE- open)
Appear to be valid
RTDIN+ shorted low Near zero
D2 Overvoltage or undervoltage fault Any protected input voltage >V
DD
or <GND1 Indeterminate
FAULT
STATUS
BIT SET
DESCRIPTION OF POSSIBLE
CAUSE
CONDITION DETECTED
DESCRIPTION OF
RESULTING DATA
D7
Open RTD element
Measured resistance greater than High Fault
Threshold value
Full scale
RTDIN+ shorted high and not
connected to RTD
Force+ shorted high and
connected to RTD
D6
RTDIN+ shorted to RTDIN-
Measured resistance less than Low Fault
Threshold value
Near zero
RTDIN+ shorted low and not
connected to RTD
Force+ shorted low
D5
Open RTD element
V
REFIN
- > 0.85 x V
BIAS
Full scale
Force+ shorted high and
connected to RTD
Force+ unconnected
Indeterminate
Force+ shorted high and not
connected to RTD
RTDIN- shorted high
D4 RTDIN- shorted low V
REFIN
- < 0.85 x V
BIAS
(FORCE- open) Appear to be valid
D3
Force+ shorted low
V
RTDIN
- < 0.85 x V
BIAS
(FORCE- open)
Near zero
RTDIN+ shorted low and
connected to RTD
RTDIN- shorted low Appear to be valid
D2 Overvoltage or undervoltage fault Any protected input voltage >V
DD
or < GND1 Indeterminate