The NDB LRM-10 is a high-precision micro-ohmmeter designed for measuring low resistance across various applications. It is a portable device, weighing 0.86 kg, with dimensions of 203 x 114 x 51 mm, making it suitable for field use. The instrument features an LCD display (128 x 64 pixels) for clear data presentation.
Function Description:
The LRM-10 micro-ohmmeter is primarily used for accurate low resistance measurements. Its applications include testing circuit breakers, soldering connections, connectors, wires, metal plates, battery inter-cell connections, and Cadweld® exothermic soldering. The device employs a four-terminal measurement technique to ensure high precision.
Important Technical Specifications:
- Measuring Range: 0.01 µΩ to 200 Ω
- Current: 10A, 250mA, 5mA
- Resolution: 0.01 µΩ
- Power Supply: Six AA NiMH rechargeable batteries
- Autonomy (number of measurements): 12,000 at 10A, 10,000 at other currents. Note that using the instrument below 0°C or with longer cables may shorten battery duration, though accuracy remains unaffected.
- Operating Temperature: -20°C to 50°C
- Charging Temperature: 0°C to 50°C
- Storage Temperature: -40°C to 50°C
- Humidity: 0 to 95% non-condensing
Scales and Accuracy:
The LRM-10 offers various scales with specified measurement errors and common mode reject errors:
- 200 Ω (5mA): 0.1% ± 2 counts, 0.02 Ω
- 20 Ω (5mA): 0.1% ± 2 counts, 0.002 Ω
- 2 Ω (250mA): 0.1% ± 2 counts, 0.0002 Ω
- 200 mΩ (250mA): 0.1% ± 2 counts, 0.02 mΩ
- 20 mΩ (10A): 0.1% ± 2 counts, 0.002 mΩ
- 2 mΩ (10A): 0.1% ± 2 counts, 0.0002 mΩ
- 200 µΩ (10A): 0.1% ± 2 counts, 0.02 µΩ ± 2 counts, 0.02 µΩ
- 20 µΩ (10A): 0.1% ± 2 counts, 0.02 µΩ ± 2 counts, 0.02 µΩ
Usage Features:
Controls and Display:
The device features a user-friendly interface with several buttons and an LCD display:
- Probe connector: For connecting measurement probes.
- Charger & RS232 communication port: Used for battery charging and data transfer to a computer.
- I/O button: To turn the instrument ON or OFF.
- Backlight button: To activate the display backlight.
- Mode button: To change the measurement mode.
- Display: LCD screen showing measurement data.
- Go button: To initiate a new measurement.
- Battery compartment: Houses the recommended rechargeable batteries.
Settings:
The LRM-10 allows users to adjust several settings:
- Frequency: Selectable between 50Hz or 60Hz to reduce reading errors caused by electromagnetic induction on test leads.
- Language: English or French.
- Contrast: Adjustable display contrast.
To access settings, press and hold the MODE button for approximately 6 seconds until the System Menu appears. Use the MODE button to select parameters and the Backlight or GO button to set them.
Operation:
- Connecting Test Leads: Ensure test leads are connected to the proper color-coded connectors on the LRM-10.
- Current and Voltage Clips: Yellow and green clips are for current injection, applying a pulsed current. Red and black clips are for voltage measurement, measuring the voltage drop across the resistance between them.
- Starting a Measurement: Press the GO button on the keypad or momentarily short the blue and green connectors (for integration into complex systems).
- Bad Connection Indicator: If a "BAD CONNECTION" error message appears, check the quality of contact for each clip.
Measurement Modes:
The LRM-10 offers five measurement modes:
- Standard mode: Displays the resistance measurement.
- Relative mode: Measures resistance relative to a previously set standard measurement. The display shows the difference between the current reading and the reference.
- Relative % mode: Similar to relative mode, but displays the resistance difference as a percentage.
- Motor mode: Measures winding resistance in a very small coil, adjusting the output's duty cycle to saturate the measured coil.
- OK/X mode: Compares the current reading to a previously taken standard measurement. If the new reading is within acceptable limits, it displays "OK"; otherwise, it displays "X".
Accessories and Spare Parts:
A wide range of accessories enhances the LRM-10's versatility:
- NDB-HSC: Hard shell case for protection.
- DRM-4014: Nylon mesh protective bag.
- DRM-403: Set of standard measuring cables with clips.
- DRM-4015: Double hands probe with replaceable tips.
- DRM-4015-2MM: 2MM tip for DRM-4015 or LRM-4015HD, for limited space applications.
- DRM-4015-SP: Long spring pin adapter for DRM-4015 and LRM-4015HD, for limited space applications.
- DRM-4040-: Set of four pins for DRM-4015 and LRM-4015HD.
- LRM-4015HD: Dual hand test probe, heavy-duty version, with replaceable tips.
- DRM-4017-19: Kelvin clamps 19mm (3/4") for measuring resistance on cables, rods, or metallic surfaces.
- DRM-4017-35: Kelvin clamps 35mm (1 3/8") for similar applications.
- DRM-4012: Exothermic welding test probe (Cadweld® test) for repeatable readings.
- DRM-4013: Sample resistance 9.5 micro-ohm, used in relative mode to set a reference value. Note: These samples are not for validating instrument precision.
- GET-40: Temporary ground cable test set.
- GET-401: Torque wrench and socket for GET-40.
- XDP-103 and XDP-104: Data transfer kit (cable and RS232 to USB converter).
- NDB-BAT: Battery replacement kit for LRM-10.
Maintenance Features:
Probe Tip Replacement:
After extensive use, probe tips may round, leading to poor electrical contact. Tips on DRM-4015 and LRM-4015HD probes are replaceable. To replace, gently pull out the old pins using long nose pliers and insert new pins using the same technique.
Protection and Transport:
The DRM-4014 nylon mesh bag and NDB-HSC transportation case are available to protect the LRM-10 micro-ohmmeter from water, dirt, and impacts, helping to preserve the instrument.
Data Transfer:
The LRM-10 can send measurement data to a computer via its serial communication port. The XDP-103 and XDP-104 data transfer kit (cable and RS232 to USB converter) is required.
- Connect the LRM-10 to the PC using the kit.
- In Windows, open the Device Manager to configure the serial port:
- Bits per second: 19200
- Data bits: 8
- Parity: None
- Stop bit: 1
- Flow control: None
- Start your preferred serial communication software.
- Begin measurements on the LRM-10, and the values will be displayed in the software.
Batteries:
The LRM-10 uses six AA type NiMH rechargeable batteries.
- It is strongly recommended to use only the battery model sold by NDB Technologies, as the charging circuit is designed specifically for this model. Using other battery models can cause excessive heat, damage, fire, or explosion.
- When replacing batteries, ensure correct polarity.
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