LTC2983
45
2983fc
For more information www.linear.com/LTC2983
APPLICATIONS INFORMATION
Fault Reporting – Thermistor
Each sensor type has unique fault reporting mechanism in-
dicated in the upper byte of the data output word. Table 54
shows faults reported during the measurement of
thermistors.
Bit D31 indicates the thermistor or R
SENSE
is open, shorted,
or not plugged in. This is a hard fault and –999°C is re-
ported. Bit D30 indicates a bad ADC reading. This could be
a result of either a broken (open) sensor or an excessive
noise event (ESD or static discharge into the sensor path).
This is a hard error and –999°C is output. In the case of
an excessive noise event, the device should recover and
the following conversions will be valid if the noise event
was a random infrequent event. Bits D29 and D28 are not
used for thermistors. Bits D27 and D26 indicate the read-
ing is over or under temperature limits (see Table 55). The
calculated temperature is reported, but the accuracy may
be compromised. Bit D25 indicates the absolute voltage
measured by the ADC is beyond its normal operating range.
If a thermistor is used as the cold junction element, any
hard or soft error is flagged in the thermocouple result.
Table 54. Thermistor Fault Reporting
BIT FAULT ERROR TYPE DESCRIPTION OUTPUT RESULT
D31 Sensor Hard Fault Hard Open or Short Thermistor or R
SENSE
–999°C
D30 Hard ADC-Out-of-Range Hard Bad ADC Reading (Could Be Large External Noise Event) –999°C
D29 Not Used for Thermistors N/A Always 0 Valid Reading
D28 Not Used for Thermistors N/A Always 0 Valid Reading
D27 Sensor Over Range* Soft T > High Temp Limit Suspect Reading
D26 Sensor Under Range* Soft T < Low Temp Limit Suspect Reading
D25 ADC Out-of-Range Soft ADC Absolute Input Voltage Is Beyond ±1.125 • V
REF
/2 Suspect Reading
D24 Valid N/A Result Valid (Should Be 1) Discard Results if 0 Valid Reading
*Do not apply to custom Steinhart-Hart sensor type. Custom table thermistor over/under range is determined by the resistor table values, see custom
thermistor table example for details.
To Next Page
Loading...