Readings from 1 µΩ to 200 Ω with category-leading accuracy
PDRM-1A
Ohmmeters
PDRM-1A
1 A digital micro-ohmmeter
Measuring very low resistances by the four-point Kelvin method, in the field and in the laboratory.
Fully automatic micro-ohmmeter
The PDRM-1A is a fully automatic digital micro-ohmmeter: it selects its own range and injects up to 1 A DC to read resistances from 1 µΩ to 200 Ω, with an accuracy of 0.1% of reading ± 2 counts and a resolution of 1 µΩ over 4¾ digits. The rugged, sealed and light unit — 0.86 kg — suits both site work and bench testing.
Four points, zero contact uncertainty
Two conductors inject the current at the ends of the joint while another two read the voltage drop directly across the section under test, so the resistance of the contacts stays out of the measurement. The microprocessor cancels offset and parasitic voltages, and the heavily filtered inputs keep the reading stable even in the presence of strong magnetic fields.
Main features
- Three test currents — 1 A, 100 mA and 5 mA — automatically adjusted.
- Standard and differential operating modes, comparing against a stored reference.
- 128 × 64 pixel LCD display with two-level backlight.
- Low current injection for applications with small measuring contacts.
- Six rechargeable NiMH AA batteries: over 4000 measurements at 1 A.
- Automatic shutdown after 2 minutes; the backlight switches off after 30 seconds.
Applications and accessories
Applications
- Checking earth connections and power busbars with the relative measurement mode.
- Verification of welded joints made with high current and of mechanical connections.
- Testing circuit-breaker contacts and power fuses.
- Quality control of castings and electrodes.
- Non-destructive verification of exothermic welds in substations.
Example: inspecting earthing grids
The earth connections used for de-energised work are the main safety guarantee for field crews. With the relative mode, the PDRM-1A stores the reading from a reference connection and compares every new measurement with it, showing the deviation — a fast way to decide whether each point of the grid is acceptable.
Accessories
- Dual hand probes with replaceable spring-loaded tips (122 cm; heavy-duty version up to 3 m).
- 35 mm booster-type and 19 mm dolphin-type Kelvin clamps.
- Dedicated probe for exothermic welds; cable-elbow accessory.
- 9.5 µΩ reference resistance to validate the unit before work.
- Nylon pouch, 46 × 35 × 18 cm rigid case and custom-length cables.
| PDRM-1A — MEASUREMENT DATA | |
|---|---|
| Measurement range | 1 µΩ to 200 Ω, with automatic range selection |
| Test currents | 1 A, 100 mA and 5 mA DC, automatically adjusted |
| Resolution | 1 µΩ; 4¾ digits |
| Accuracy | 0.1% of reading ± 2 counts |
| Measurement method | Four-point Kelvin |
| Operating modes | Standard and differential (comparison with a stored reference) |
| Signal processing | Offset and parasitic voltage suppression; inputs filtered against magnetic fields |
| Autonomy | Over 4000 measurements at 1 A; over 10,000 at the other currents |
PDRM-1A — TECHNICAL SPECIFICATIONS
| Display | 128 × 64 pixel LCD, 60 × 41 mm |
|---|---|
| Backlight | Two levels (100% and 50%); switches off after 30 seconds |
| Power supply | Six rechargeable NiMH AA batteries |
| Power management | Automatic shutdown after 2 minutes of inactivity |
| Operating temperature | -20 to +50°C |
| Storage temperature | -40 to +50°C |
| Humidity | 0 to 95%, non-condensing |
| Enclosure | Sealed and shock-resistant |
| Dimensions | 203 × 114 × 51 mm |
| Weight | 0.86 kg |
| Kit | Micro-ohmmeter, Kelvin clamps, AA batteries, manual and calibration certificate |