LM Series High Precision Plate Resistors
High precision plate resistive element in leaded through-hole package
Power rating 1/8W to 1W
Resistance range 500kΩ to 1GΩ — extending precision into the ultra-high-resistance region
Plate construction — elongated resistive track on flat substrate for stable high-value film formation
Leaded terminations — compatible with through-hole PCB assembly and guarded circuit layouts
Tolerance options ±0.1%, ±0.25% and ±0.5%
TCR options 25, 50 and 100 ppm/°C
Stable resistance value across temperature — controlled film geometry for consistent TCR
Suitable for electrometer, ion measurement and ultra-high-impedance circuit applications
What are the LM Series High Precision Plate Resistors?
The LM is a high precision leaded plate resistor covering the ultra-high-resistance range from 500kΩ to 1GΩ, a region that presents fundamental construction challenges for resistor manufacturers and that is inaccessible to wire wound technology altogether. At resistance values approaching and exceeding 1GΩ, the resistive element must be physically long relative to its width to achieve the required sheet resistance without relying on resistive pastes so highly loaded with insulating binders that TCR, voltage coefficient, and long-term stability all degrade to unacceptable levels. The plate construction of the LM addresses this by forming an elongated resistive track on a flat substrate — maximising the length-to-width ratio of the resistive path within a manageable component body — and thereby enabling the combination of gigaohm-range resistance values and the tight tolerances of ±0.1% to ±0.5% that the series offers.
The LM sits in a distinct position within RARA Electronics’ precision resistor portfolio. The wire wound series — 5G10, 8G16/8G24, GG102, AX, and CE-CL-T — provide the tightest tolerances and lowest TCR values available at resistance values up to approximately 1.5MΩ, but wire wound construction cannot extend into the gigaohm range due to the impractical wire lengths that would be required. The SM thin film chip resistor covers the same 500kΩ to 1GΩ resistance range in an SMD format for automated board assembly, while the LM provides the same resistance coverage in a leaded package suited to circuits where through-hole mounting, guarded PCB layout, and direct connection to coaxial or triaxial shielded wiring are requirements of the measurement system. Together the LM and SM give designers a choice of package for ultra-high-resistance precision applications without compromise on the resistance range.
Three tolerance grades are available at ±0.1%, ±0.25%, and ±0.5%, with TCR options of 25, 50, and 100 ppm/°C. In the gigaohm resistance range, even a 100 ppm/°C TCR represents a resistance change of only 0.01% per degree Celsius — a level of stability that is difficult to achieve in this resistance range and that demands careful control of both the resistive film composition and the geometry of the plate element. The power rating of 1/8W to 1W is more than sufficient for the signal-level currents that flow in ultra-high-resistance circuits, where even at 1GΩ a full 1W dissipation would require 31,623V across the resistor — far beyond the operating voltage of signal-level measurement circuits.
RARA Electronics holds ISO 9001 and IATF 16949 certifications, and the LM series is manufactured to the same quality standards relied upon by major industrial, instrumentation, and metrology customers globally. Comparable ultra-high-resistance precision types in leaded packages are specified wherever engineers need a stable, accurate, and repeatable resistance in the megaohm-to-gigaohm range — applications that conventional precision resistors simply cannot reach.
LM Series High Precision Plate Resistors Specifications
A practical overview for engineers and procurement teams evaluating resistive solutions.
Model: LM
Resistor type: High precision
Description: Plate
Power Rating: 1/8W-1W
Resistance (Ω): 500k~1G
Tolerance (%): ±0.1, ±0.25, ±0.50
TCR (ppm/C): 25, 50, 100
Applications of the LM Series High Precision Plate Resistors
Where RARA precision resistors are deployed in the field.
Electrometer input and feedback resistors — the feedback resistor of an electrometer operational amplifier defines the current-to-voltage conversion ratio directly; at femtoampere-to-picoampere input current levels the feedback resistance must be in the gigaohm range to produce a measurable output voltage, and the LM provides the precision and stability required for calibrated electrometer circuits used in semiconductor characterisation, ion beam measurement, and nuclear particle detection
pH meter and ion-selective electrode reference circuits — the input impedance of pH and ion electrode amplifiers must exceed the source impedance of the glass membrane electrode, which can reach hundreds of megaohms; precision gigaohm resistors in the input network set the bias current path and define the common-mode rejection of the differential amplifier without introducing resistance error that would shift the pH calibration
Insulation resistance measurement circuits — precision voltage dividers and reference resistors in insulation testers, megohmeters, and dielectric analyser circuits where the measurement range extends into the gigaohm region and where the accuracy of the reference resistance determines the accuracy of the insulation resistance reading
Ultra-high-impedance voltage measurement — guarded input attenuators and voltage divider chains in electrometers and high-impedance voltmeters where the resistor divider ratio must be stable and accurate at values that would load or disturb the high-impedance source under measurement; the leaded package of the LM facilitates integration into guarded PCB layouts with driven guard rings that eliminate surface leakage current around the high-impedance node
Radiation detection and nuclear instrumentation — charge-sensitive preamplifier feedback resistors and bias supply decoupling resistors in radiation detector circuits, where the feedback resistor in the range of tens to hundreds of megaohms determines the shaping time constant of the detector pulse and must remain stable across the temperature range of the measurement environment
Mass spectrometer ion current measurement — transimpedance amplifier feedback resistors in Faraday cup detector circuits where the ion current to be measured is in the femtoampere-to-nanoampere range and where the feedback resistance of 10MΩ to 1GΩ sets the sensitivity and dynamic range of the measurement channel
Leakage current and surface insulation resistance testing — reference resistors in printed circuit board surface insulation resistance testers, capacitor leakage measurement equipment, and diode reverse leakage characterisation fixtures where the reference must be stable and accurate in the megaohm-to-gigaohm range to provide a calibrated comparison against the unknown leakage resistance
High-voltage divider bleeder and biasing resistors — lower arms of precision voltage divider chains in high-voltage measurement probes and oscilloscope probe heads where the lower resistor is in the megaohm range and where its tolerance and TCR directly determine the division ratio accuracy and temperature drift of the probe over its operating temperature range
Photodiode and photomultiplier tube bias and load networks — load and quench resistors in light detection circuits operating at very low photocurrent levels, where the load resistance in the gigaohm range maximises transimpedance gain and sensitivity while the precision tolerance of the LM ensures that the gain calibration of the optical measurement system is consistent across production units
Medical and scientific precision instrumentation — ultra-high-impedance signal conditioning circuits in bioelectric measurement equipment, patch clamp amplifiers for single-cell electrophysiology, and chemical sensor interfaces where the source impedance of the biological or chemical transducer can reach hundreds of megaohms and where the precision and stability of the input network resistors directly determine the measurement accuracy of the instrument
Related Products of the LM Series High Precision Plate Resistors
Model: RMF
Resistor type: Precision
Description: High power 4 terminal
Power Rating: 10W
Resistance (Ω): 0.5~200
Tolerance (%): ±0.1~±5
TCR (ppm/C): 5, 10, 15, 20, 30
Model: 400 Series
Resistor type: High Voltage
Description: Precision, Non-Inductive
Low TCR
Power Rating: 3.8W~20W
Supply voltage: 15kV~90kV
Resistance (Ω): 1k~1T
Tolerance (%): ±0.05 to ±10
TCR (ppm/C): 5, 10, 15, 25, 50, 100
Model: GG102
Resistor type: Precision
Description: Wire wound
Power Rating: 0.3W
Resistance (Ω): 10~250k
Tolerance (%): ±0.01, ±0.1
TCR (ppm/C): 3
Model: RH/RHF
Resistor type: Precision
Description: High power wire wound
Power Rating: 1W~50W
Resistance (Ω): 1m~600k
Tolerance (%): ±0.01, ±1
TCR (ppm/C): 30, 50, 100
Why Choose RARA Precision Resistors
What sets RARA apart for engineers and procurement managers in industrial and automotive markets.
01
Extreme Accuracy
Tolerances as tight as ±0.005% and TCR as low as 3 ppm/°C — across metal film, thin film chip, wire wound, and MELF construction types to suit every precision circuit requirement.
02
Long-Term Stability
Precision resistors are only useful if they stay accurate. RARA precision types are engineered for extended load life — maintaining resistance within specification over thousands of hours of operation.
03
Full Technology Range
From 1/32W SMD thin film chips to 50W high-power precision wire wound types — one precision resistor family covering every power level and form factor from a single ISO-certified supplier.
04
Global Track Record
Trusted by Toshiba, Siemens, Rockwell, LG, and Schneider Electric — deployed in instrumentation, medical, and industrial measurement systems across six continents.
