CL940A 500 Hour Thermocouple Calibrator with 0.01° Resolution
Industrial Thermocouple Handheld Calibrator
Supported Applications
The Omega CL940 Series functions as a digital temperature calibrator and thermometer designed for thermocouples, RTDs, thermistors, and millivolt (mV) signals. The series supports calibration tasks across standard ITS-90 types B, E, J, K, N, R, S, T, along with ASTM E1751 Type G, DIN 43710 Types L and U, ASTM E286 Table 3 Type D, and ASTM E1751 5.1.2 Type P.
Operating Conditions & Performance
The CL940 Series delivers a source/measure accuracy of ±0.003% * [READING] ± 5μV at ambient temperatures between 18°C and 28°C, with an included cold junction error (CJC) of ±0.15°C. Resolution is specified as 0.01°C up to 999.99°C and 0.1°C for readings ≥ 1000°C. The instrument operates on a voltage range of -15mV to 85mV with a reading rate of 3/sec for both Readings and TREND indicators.
Accuracy varies by thermocouple type and temperature span, as documented in the specification tables:
• Type K: ±0.2°C (380 to 665°C) through ±1.2 to ±0.6°C (-230 to -90°C)
• Type J: ±0.2°C (10 to 1200°C) through ±0.7 to ±0.5°C (-200 to -160°C)
• Type T: ±0.2°C (80 to 400°C) through ±2.6 to ±0.7°C (-260 to -190°C)
• Type E: ±0.2°C (20 to 1000°C) through ±1.2 to ±0.4°C (-240 to -150°C)
Additional types B, N, R, S, C, D, G, P, L, and U are supported with specific accuracy bands defined by temperature range in the source documentation.
Configuration Options
• Sensor Types: Supports Thermocouple (Types B, E, J, K, N, R, S, T), RTD, Thermistor, and mV inputs. Models CL940A and CL945A are covered; the CL945A supports additional thermocouple types including B, N, R, S, C, D, G, L, U.
• Display & Interface: Features a 2-row, 5-digit LCD with auto-resolution (0.1/0.01), backlight, and function annunciators for offset, thermocouple types, battery status, source/read modes, temperature units, voltage units, percent, trend, PRST (0-19), MIN, MAX, AVG, RNG, STDEV, Transfer symbols, Fast Ramp, Slow Ramp, Step, and Bluetooth.
• Statistics & Storage: Includes Minimum Reading, Maximum Reading, Average Reading, Reading Range, Standard Deviation calculations. Internal preset storage provides 20 user-determined registers (0-19).
• Power Management: Powered by three AA batteries (IEC LR6, ANSI 15 Alkaline) with a typical life of 500 hours and a four-stage battery charge indicator. Auto-off activates after 20 minutes of no key press but can be disabled.
• Connections: Utilizes two Mini-TC Copper connectors for electrical connection.
Key Product Differences
The series comprises two primary models: CL940A and CL945A. The distinction lies in thermocouple type support; the CL945A model includes capability for Types B, N, R, S, C, D, G, L, U, whereas these types are not supported on the standard configuration without this specific variant designation.
Both models retain power cycle configurations including Sensor Type, Temperature Unit Offset Values, Presets, Statistics, Open Lead detection status, 0%/100% span settings, and operating mode. The instrument conforms to EN 60584-1:2013 for standard types and specific ASTM/DIN standards for extended types.
| Additional Features 1 | Read and Source Signals |
| Auto Off | 20 min |
| Auto Off Note | 20 minute no key pressed Auto Off. Feature can be disabled |
| Battery Indication | 4 stage battery charge indication |
| Battery life | 500 hr |
| Cold Junction Error | ± 0.15 °C |
| Common Mode Voltage | 42 V |
| Common Mode Voltage (CJC error), Max | 1 V |
| Common Mode Voltage Note | 42 V peak to earth; 1 V p-p between T1 and T2 |
| Dimensions (CJC error) | 7.6 L x 3.3 W x 1.1 H in |
| Display Backlight | Four (4) LED Backlight with 30-second timeout |
| Display Resolution | 0.01° |
| Display Resolution (CJC error) | 0.1° |
| Display Type | Backlit LCD |
| Display Type Note | 5-DIGIT AUTO-RESOLUTION (0.1/0.01) WITH BACKLIGHT AND FUNCTION ANNUNCIATORS Two (2) rows of Five (5) digit LCD with separate minus sign, decimal indicators, with offset, thermocouple types KJTEBNRSGCDPLU, battery, source, read, temperature units, voltage units, percent, trend, PRST (0-19), MIN, MAX, AVG, RNG, STDEV, Transfer, symbols: Fast Ramp, Slow Ramp, Step, Bluetooth |
| Electrical Connection | Miniature Female Thermocouple Connector |
| Height | 28 mm |
| Input Current | ± 50 nA |
| Internal Preset Storage | 20 user defined presets available |
| Keypad | 12 Switches |
| Length | 193 mm |
| Low Resistance Load | Less than 5µV change in output with a 100KΩ resistance |
| Millivolt Range | -15 to 85 mV |
| Operating Environment | Altitude: 0 to 4600 m ; 0 to 15,092 ft(CJC Error) Vibration: Random 10 – 500 Hz; 0.03 g2/Hz(CJC Error) Shock: 30g Half Sine Drop: 4 Drops from 1 m to Concrete |
| Operating Temperature, Max | 55 °C |
| Operating Temperature, Min | -20 °C |
| Operating Temperature Note | Operating Temperature(CJC error): -4 to 131°F |
| Power Cycle Configuration Retention | Instrument retains: Sensor Type, Temperature Unit Offset Values, Presets, Statistics, Open Lead detection status, 0%/100% span settings, and operating mode |
| Probe Offset Uncertainty | Resolution 0.1 °C/°F |
| Reading Rate | 3/sec |
| Reading Rate Note | 3/sec. for Readings and TREND indicators |
| Relative Humidity, Max | 0.95 |
| Relative Humidity, Min | 5% |
| Relative Humidity Note | <10 °C (50 °F): Non-condensing 10 to 30 °C (50 to 86 °F): 5 to 95% RH 30 to 40 °C (86 to 104 °F): 5 to 85% RH 40°C to 55°C (104 to 131 °F): 5 to 60% RH |
| Resolution, Max | 999.99 °C |
| Resolution, Min | 0.01 °C |
| Resolution Note | 0.01°C UP TO 999.99°C AND 0.1°C ≥ 1000°C |
| Sanitation | NSF, ANSI/3-1 14159-2 |
| Series ID | CL940-Series |
| Storage Temperature, Max | 71 °C |
| Storage Temperature, Min | -51 °C |
| Storage Temperature Note | Storage Temperature(CJC error): -59.8 to 159.8°F |
| Supply Voltage | 4.5 Vdc |
| Temperature Coefficient | For specification variances due to ambient operating temperature, see the Expanded Instrument Uncertainty charts in Appendix B of this manual. For ambient operating temperatures not shown in Appendix B, accuracies shall be interpolated linearly. |
| Weight | 362.9 g |
| Weight (CJC error) | 12.8 oz (including batteries) |
| Weight Note | 362.9g (including batteries) |
| Width | 84 mm |