Measurement Computing WEB-TC - Manual (Page 28)

28
Chapter 6
Specifications
Typical for 25 °C unless otherwise specified.
Specifications in italic text are guaranteed by design.
Analog input
Table 1. Generic analog input specifications
Parameter Conditions 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
power supply input.
Channel configuration Software programmable to match sensor type
Differential input voltage
range Thermocouple ±0.080 V
Absolute maximum input
voltage ±C0x through ±C7x relative to
AGND (pins 9, 19, 28, 38) ±25 V (power on)
±40 V (power off)
Input impedance 5 Gigohm (power on)
1 Mohm (power off)
Input leakage current Open thermocouple detect disabled 30 nA max.
Open thermocouple detect enabled 105 nA max.
Common mode rejection ratio f
IN
= 60 Hz 100 dB min.
ADC Resolution 24 bits
ADC No missing codes 24 bits
Input coupling DC
Warm-up time 30 minutes min.
Open thermocouple detect The maximum open detection time is 3 seconds.
CJC sensor accuracy 15 °C to 35 °C -0.75 °C to 0.5 °C max.
0 °C to 55 °C -1.5 °C to 1.25 °C max.
Channel configurations
Table 2. Channel configuration specifications
Sensor Category Conditions Specification
Thermocouple J, K, S, R, B, E, T, or N 8 differential channels
Note 1: Channel configuration information is stored on a EEPROM external to the isolated microcontroller by
the firmware whenever any item is modified. Modification is performed by commands issued over
Ethernet 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.