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Simpson’s high precision Model 444-2 has been redesigned for added ESD immunity and longer battery life. The model 444-2 Micro-Ohmmeter measures resistance from 50 micro-ohm to 20 ohms. It measures using an extremely small test voltage (100 microvolt maximum) and a four wire measurement technique. The resistance reading is indicated on a 4- 1/2 digit LCD display using one of two measuring modes: An automatic AC measurement mode or a manual DC measurement mode. By limiting the test voltage of the Model 444-2 to only 100 micro volts the instrument will not "punch through" contamination or corrosion. An audible tone can be used to indicate resistance values below any selected reading. The Model 444-2 has a universal power input range of 85Vac to 250Vac and incorporates a self-contained rechargeable Ni-Cad battery for field use.
| Range | Resolution | Maximum Test Current |
| 20mΩ | 1μΩ | 5mA |
| 200mΩ | 10μΩ | 500μA |
| 2Ω | 100μΩ | 50μA |
| 20Ω | 1mΩ | 5μA |
| Accuracy | ± (0.05% of input ± 600 counts) DC mode ± (0.05% of input ± 15 counts) AC mode |
| Alarm | Resistance below set point activates audible beeper and display annunciator. Resistance above set point activates display annunciator |
| Set Point Adjustment | Front Panel Knob |
| Set Point Accuracy | ± (2% of input +150 counts) |
| Maximum Test Voltage | 100μV peak |
| Measurement Techniques | (AC) Pulse of 50 Hertz Square Wave and DC Switchable Polarity |
| Display | 19,999 counts, 4.5 digits LCD type, 0.5" high, and "AC," "DC" and " annunciators |
| Conversion Rate | Reading 2 per second |
| Test Leads | BNC to dual Kelvin clip (2 leads) RG-58 |
| Operating Voltage | 85VAC to 250VAC, 10VA maximum |
| Operating Temperature Range | 0° to 50°C |
| Storage Temperature Range | -40° to +60°C |
| Relative Humidity | 90% maximum up to 35°C, 70% maximum up to +50°C (non-condensing) |
| Temperature Coefficient | 0.2%/°C (0° to 18°C and 28° to 50°C) |
| Extended Battery Life | Typical 10 hours |
| Battery Mode Rated Circuit-To-Ground Voltage | 30V (RMS) |
| Display Settling Time | <15 seconds |
| Dimensions | 2.7" x 8.4" x 9.0" (68 x 213 x 228 mm) nominal |
| Weight | Approximately 3 Ibs. |
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