Thin-film technology allows the HFM series sensor to be the fastest heat flux sensor on the market, with an uncoated response time of 17 microseconds. The thermopile construction measures radiation and convection equally well with a 180° field-of-view. Each HFM has a temperature measurement for signal compensation.
| HFM | HFM-6D/H | HFM-7E/H | HFM-7E/L | HFM-8E/L | HFM-8E/H |
| Time Response (µs) uncoated (coated) | 17 (300) | 17 (300) | 17 (300) | 17 (300)* | 17 (300)* |
| Minimum Sensitivity (µV/W/cm²) | 10 | 150 | 150 | 150 | 150 |
| Max Face Temperature (°C)** | 800 | 600/400 | 350 | 350 | 350 |
| Metallurgy | Platinum Platinum-Rhodium | Nichrome Constantan | Nichrome Constantan | Nichrome Constantan | Nichrome Constantan |
| Temperature Sensor | Surface RTD | Surface RTD | Surface RTD | Thermocouple in body | Thermocouple in body |
| Housing material | Nickel | Nickel | Copper & Brass | Copper & Brass | Nickel |
| Cable | Mineral sheath | Mineral sheath | Teflon coated | Teflon coated | Mineral sheath |
| Calibration Accuracy: | ±3% | ±3% | ±3% | ±3%* | ±3%* |
| Repeatability: | 2% | 2% | 2% | 2% | 2% |
* Time response to heat flux only, temperature response for thermocouple measurements may lag depending on heat sink conditions. Large lags in temperature response may affect accuracy. **Max face temperature listed; max cable temperature is 600°C for E/H units and 200°C for others. HFM-7E/H and HFM-8E/H max face temperature lists short term and continuous use temperature respectively.
For more information on HFM operation and mounting diagrams, see the HFM User's Guide
HFM-1000 Series Water-Cooled High-Speed Thermopile Heat Flux Sensors
Water-cooled sensors have an active heat sink and so are less sensitive to mounting conditions, especially for applications with longer measurement times or high heat flux levels. The HFM-1000 series sensors take a standard HFM-7E or HFM-8E substrate and put it into a water-cooled body, which are identical to the Thermogage 1000 series gauges except for the sensing element.
HFM-9000 Series Water-Cooled High-Speed Thermopile Radiometers
Vatell radiometers are our standard heat flux sensor with a window in front of the sensing element to screen out convection so that only radiation is measured. Most radiometer applications will use a Thermogage sensing element, but for those needing response times as fast as 300 microseconds an HFM sensing element can be used in a Thermogage 9000 series body. The window is placed directly on the water-cooled copper surface to minimize its heating, but is not in contact with the sensing element itself. Sapphire is the standard window material with a spectral range of 0.3-5 microns; its hardness and chemical resistance let it stand up to the harshest environments. ZnSe (0.6-17 micron range) and other materials are available upon request.