Features and Benefits
- Low cost and easy to use
- Pretrimmed for J type thermocouples
- Internal cold junction compensation
- High impedance differential input
- Standalone 5 mV/°C thermometer
- Reference pin allows offset adjustment
- Thermocouple break detection
- See data sheet for additional features.
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
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
This user guide is a description of functionality for the AD8494 series evaluation board. The evaluation board can be configured for the AD8494, AD8495, AD8496, and AD8497 to ensure that the metals and alloys are properly matched for the thermocouple type for which the device is trimmed. The 4-layer evaluation board is designed to allow users to quickly prototype the precision thermocouple amplifiers for various user defined configurations for different applications. The evaluation board has three modes of operation: linear mode, setpoint controller mode, and hysteresis on setpoint controller mode.
The AD8494/AD8495/AD8496/AD8497 data sheet is available at www.analog.com. This data sheet provides additional information on the AD8494, AD8495, AD8496, and AD8497 and must be consulted in conjunction with this user guide when using the evaluation board.
Documentation & Resources
UG-1421: AD8494 Series Evaluation Board11/20/2019
AD849x Series: Thermocouple Amps with Cold Junction Compensation7/9/2021
Thermocouple 101: Filtering a Thermocouple6/3/2019
Thermocouple 101: Open Thermocouple Detection6/3/2019
Thermocouple 101: Setting the Common Mode Voltage6/3/2019
Thermocouple 101: Measuring the Tiny Signal6/3/2019
Thermocouple 101: Cold Junction Compensation6/3/2019
Thermocouple 101: What is a Thermocouple?6/3/2019
Thermocouple 101: Compensating for Nonlinearity6/3/2019
Thermocouple 101: Thermocouple Nonlinearity6/3/2019
Bits Per Second Make My Head Hertz1/1/2014
RAQs: 100 Issues and Counting12/1/2013
Electronics is Fun1/1/2013
The Decline of Rounding—or How Significant is Significance?12/1/2012
Current Transformers—and Vacuum Cleaners10/1/2012
Great Expectations Come From Basic Understandings9/1/2012
Driving Miss ADC8/1/2012
How to Avoid Burning Cakes6/1/2010
Bring on the Converter Noise! – Part 212/1/2009
Tools & Simulations
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.