AD594 Type J Thermocouple Amplifier with Cold Junction Compensation

The AD594/AD595 is a complete instrumentation amplifier and thermocouple cold junction compensator on a monolithic chip. It combines an ice point reference with a precalibrated amplifier to produce a high level (10 mV/°C) output directly from a thermocouple signal. Pin-strapping options allow it to be used as a linear amplifier-compensator or as a switched output setpoint controller using either fixed or remote setpoint control. It can be used to amplify its compensation voltage directly, thereby converting it to a stand-alone Celsius transducer with a low impedance voltage output.

The AD594/AD595 includes a thermocouple failure alarm that indicates if one or both thermocouple leads become open. The alarm output has a flexible format which includes TTL drive capability.

The AD594/AD595 can be powered from a single ended supply (including +5 V) and by including a negative supply, temperatures below 0°C can be measured. To minimize self-heating, an unloaded AD594/AD595 will typically operate with a total supply current 160 µA, but is also capable of delivering in excess of ±5 mA to a load.

The AD594 is precalibrated by laser wafer trimming to match the characteristic of type J (iron-constantan) thermocouples and the AD595 is laser trimmed for type K (chromel-alumel) inputs. The temperature transducer voltages and gain control resistors are available at the package pins so that the circuit can be recalibrated for the thermocouple types by the addition of two or three resistors. These terminals also allow more precise calibration for both thermocouple and thermometer applications.

The AD594/AD595 is available in two performance grades. The C and the A versions have calibration accuracies of ±1°C and ±3°C, respectively. Both are designed to be used from 0°C to +50°C, and are available in 14-pin, hermetically sealed, side-brazed ceramic DIPs as well as low cost cerdip packages.

Features and Benefits
  • Pretrimmed for Type J (AD594) or Type K (AD595) Thermocouples
  • Can Be Used with Type T Thermocouple Inputs
  • Low Impedance Voltage Output: 10 mV/°C
  • Built-In Ice Point Compensation
  • Wide Power Supply Range: +5 V to ±15 V
  • Low Power: <1 mW typical
  • Thermocouple Failure Alarm
  • Laser Wafer Trimmed to 1°C Calibration Accuracy
  • Setpoint Mode Operation
  • Self-Contained Celsius Thermometer Operation
  • High Impedance Differential Input
  • Side-Brazed DIP or Low Cost Cerdip
  • Analog to Digital Converters
    Data Sheets
    Documentnote
    AD594/AD595: Monolithic Thermocouple Amplifiers With Cold Junction Compensation Data Sheet (Rev. C)PDF 136 kB
    Application Notes
    Documentnote
    AN-214: Ground Rules for High Speed CircuitsPDF 356 kB
    AN-369: Thermocouple Signal Conditioning Using the AD594/AD595 (Rev. B)PDF 218.48 K
    AN-274: Taking the Uncertainty Out of Thermocouple Temperature Measurement (With the AD594/AD595) -PDF 643 kB
    AN-349: Keys to Longer Life for CMOSPDF 89 kB
    Order Information
    Part NumberPackagePacking QtyTemp RangePrice 100-499Price 1000+RoHS
    AD594ADZ Production14 ld Side-Brazed CerDIPOTH 25-55 to 125C22.918.83Y
    AD594AQ Production14 ld CerDIPOTH 25-55 to 125C10.849.17N
    AD594CDZ Production14 ld Side-Brazed CerDIPOTH 25-55 to 125C83.0669Y
    AD594CQ Production14 ld CerDIPOTH 25-55 to 125C16.1513.25N
    AD594/AD595: Monolithic Thermocouple Amplifiers With Cold Junction Compensation Data Sheet (Rev. C) ad594
    AN-214: Ground Rules for High Speed Circuits ad1674
    AN-349: 延长CMOS寿命的关键因素 adg3233
    AN-369: Thermocouple Signal Conditioning Using the AD594/AD595 (Rev. B) ad594
    AN-369: 利用AD594/AD595调理热电偶信号 ad594
    AN-274: 消除热电偶温度测量中的不确定性(使用AD594/AD595) (Rev. 0) ad594
    AN-274: Taking the Uncertainty Out of Thermocouple Temperature Measurement (With the AD594/AD595) - ad594
    AN-349: Keys to Longer Life for CMOS ad7703