Measurement-computing USB-5203 Instrukcja Użytkownika Pobierz pdf (Strona 22)

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 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 USB

interface

Channel configuration Software programmable to match sensor type

Differential input voltage

range for the various sensor

categories

Thermocouple ±0.080 V

RTD 0 V to 0.5 V

Thermistor 0 V to 2 V

Semiconductor sensor 0 V to 2.5 V

Absolute maximum input

voltage

±C0x through ±C7x relative to GND

(pins 9, 19, 28, 38)

±25 V power on, ±40 V power off

Input impedance 5 GΩ, min

Input leakage current Open thermocouple detect disabled 30 nA max

Open thermocouple detect enabled 105 nA max

Normal mode rejection ratio fIN = 60 Hz 90 dB min

Common mode rejection

Ratio

fIN=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 sensor.

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 °C to +0.5 °C max

Channel configurations

Internally, the device has four, dual-channel, fully differential A/Ds providing a total of eight differential

channels. The analog input channels are therefore configured in four channel pairs with CH0/CH1 sensor

inputs, CH2/CH3 sensor inputs, CH4/CH5 sensor inputs, and CH6/CH7 sensor inputs paired together. This

channel-pairing requires the analog input channel pairs be configured to monitor the same category of

temperature sensor. Mixing different sensor types of the same category (such as a type J thermocouple on

channel 0 and a type T thermocouple on channel 1) is valid.

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.

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