Measurement Computing USB-TC - Manual (Page 15)

15
Chapter 5
Specifications
All specifications are subject to change without notice.
Typical for 25 °C unless otherwise specified.
Specifications in italic text are guaranteed by design.
Analog input
Table 1. Generic analog input specifications
Parameter Condition Specification
A/D converters Four dual 24-bit, Sigma-Delta type
Number of channels 8 differential
Input isolation 500 VDC minimum between field wiring and USB
interface
Channel configuration Thermocouple sensor type
Differential input voltage
range Thermocouple ±0.080 V
Absolute maximum input
voltage ±C0x through ±C7x relative to
GND (pins 9, 19, 28, 38) ±24 V power on,
±24 V power off
Input impedance 5 GΩ, min
Input leakage current Open thermocouple detect enabled 105 nA max
Normal mode rejection ratio f
IN
= 60 Hz 90 dB min
Common mode rejection ratio f
IN
= 50 Hz/60 Hz 100 dB min
Resolution 24 bits
No missing codes 24 bits
Input coupling DC
Warm-up time 30 minutes min
Open thermocouple detect Automatically enabled when the channel pair is
configured for thermocouple sensors.
The maximum open detection time is 3 seconds.
CJC sensor accuracy 15 °C to 35 °C ±0.25 °C typ,
±0.5 °C max
0 °C to 70 °C –1.0 to +0.5 °C max
Channel configurations
Table 2. Channel configuration specifications
Sensor Category Condition Specification
Thermocouple J, K, S, R, B, E, T, or N 8 differential channels
Note 1: Channel configuration information is stored in the EEPROM of the isolated microcontroller by the
firmware whenever any item is modified. Modification is performed by commands issued over USB
from an external application, and the configuration is made non-volatile through the use of the
EEPROM.
Note 2: The factory default configuration is Type J.