Measurement Computing USB-TC-AI - Manual (Page 20)

USB-TC-AI User's Guide Specifications
20
Temperature alarms
Table 12. Temperature alarm specifications
Parameter Specification
Number of alarms 8 (one per digital I/O line)
Alarm functionality Each alarm controls its associated digital I/O line as an alarm output. The input to each
alarm may be any of the analog temperature input channels. When an alarm is enabled, its
associated I/O line is set to output (after the device is reset) and driven to the appropriate
state determined by the alarm options and input temperature. The alarm configurations are
stored in non-volatile memory and are loaded at power on. Alarms will function both in
data logging mode and while attached to USB.
Alarm input modes  Alarm when input temperature > T1
 Alarm when input temperature > T1, reset alarm when input temperature goes below T2
 Alarm when input temperature < T1
 Alarm when input temperature < T1, reset alarm when input temperature goes above T2
 Alarm when input temperature is < T1 or > T2
Note: T1 and T2 may be independently set for each alarm.
Alarm output modes  Disabled, digital I/O line may be used for normal operation
 Enabled, active high output (digital I/O line goes high when alarm conditions met)
 Enabled, active low output (digital I/O line goes low when alarm conditions met)
Alarm update rate 1 second
Counter
Table 13. CTR I/O specifications
Parameter Specification
Pin name CTR
Number of channels 1
Resolution 32-bits
Counter type Event counter
Input type TTL, rising edge triggered
Input source CTR screw terminal
Counter read/writes rates
(software paced) Counter read: system dependent, 33 to 1000 reads per second.
Counter write: system dependent, 33 to 1000 reads per second.
Schmidt trigger hysteresis 20 mV to 100 mV
Input leakage current ±1.0 µA typ
Input frequency 1 MHz max
High pulse width 500 nS min
Low pulse width 500 ns min
Input high voltage 4.0 V min, 5.5 V absolute max
Input low voltage 1.0 V max, –0.5 V absolute min
Note 13: All ground pins are common and are isolated from earth ground. If a connection is made to earth
ground with both the counter (CTR) and conductive thermocouples, the thermocouples are no longer
isolated. In this case, thermocouples must not be connected to any conductive surfaces that may be
referenced to earth ground.
Memory
Table 14. Memory specifications
Parameter Specification
EEPROM 1,024 bytes isolated micro reserved for sensor configuration
256 bytes USB micro for external application use