Full J-Type Range 25° to 100° Thermocouple Amplifier w/Cold Junction Compensation
The AD8494/AD8495/AD8496/AD8497 are precision instrumentation amplifiers with thermocouple cold junction compensators on an integrated circuit. They produce a high level (5 mV/°C) output directly from a thermocouple signal by combining an ice point reference with a precalibrated amplifier. They can be used as standalone thermometers or as switched output setpoint controllers using either a fixed or remote setpoint control.
The AD8494/AD8495/AD8496/AD8497 can be powered from a single-ended supply (less than 3 V) and can measure temperatures below 0°C by offsetting the reference input. To minimize self-heating, an unloaded AD849x typically operates with a total supply current of 180 μA, but it is also capable of delivering in excess of ±5 mA to a load.
The AD8494 and AD8496 are precalibrated by laser wafer trimming to match the characteristics of J type (iron-constantan) thermocouples; the AD8495 and AD8497 are laser trimmed to match the characteristics of K type (chromel-alumel) thermo-couples. See Table 1 on the data sheet for the optimized ambient temperature range of each part.
The AD8494/AD8495/AD8496/AD8497 allow a wide variety of supply voltages. With a 5 V single supply, the 5 mV/°C output allows the devices to cover nearly 1000 degrees of a thermo-couple’s temperature range.
The AD8494/AD8495/AD8496/AD8497 work with 3 V supplies, allowing them to interface directly to lower supply ADCs. They can also work with supplies as large as 36 V in industrial systems that require a wide common-mode input range.
- Complete, precision laser wafer trimmed thermocouple signal conditioning system in a single IC package.
- Flexible pinout provides for operation as a setpoint controller or as a standalone Celsius thermometer.
- Rugged inputs withstand 4 kV ESD and provide over-voltage protection (OVP) up to VS ± 25 V.
- Differential inputs reject common-mode noise on the thermocouple leads.
- Reference pin voltage can be offset to measure 0°C on single supplies.
- Available in a small, 8-lead MSOP that is fully RoHS compliant.
- J type thermocouple temperature measurement
- Setpoint controller
- Celsius thermometer
- Universal cold junction compensator
- White goods (oven, stove top) temperature measurements
- Exhaust gas temperature sensing
- Catalytic converter temperature sensing
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This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
Two Ways to Measure Temperature Using Thermocouples Feature Simplicity,...
(Analog Dialogue 44-10, October 2010)
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