Hitachi LPF Series Low Pass Filter Boards

Technical Dossier

Product Details And Specifications

Hitachi LPF Series: Comprehensive Module Range and Technical Overview

The Hitachi LPF Series Low Pass Filter Boards are analog signal conditioning components deployed across heavy industrial control architectures, including distributed control systems (DCS) in petrochemical refineries, nuclear power generation facilities, and large-scale chemical processing plants. The LPF Series functions as an analog signal integrity layer, attenuating high-frequency noise from field instrumentation before signals reach the controller's analog input modules. In facilities where 4–20 mA loop integrity is critical to process safety, these boards represent a non-negotiable element of the I/O subsystem. Hitachi's LPF boards are designed for direct integration into the HIDIC and EX Series control backplanes, and their long service history means a significant installed base remains active in aging plant infrastructure worldwide.

The Evolution of LPF Series Architecture

The LPF Series was introduced as part of Hitachi's analog signal management strategy for its HIDIC S10 and S10V programmable controller platforms during the late 1980s and through the 1990s. Early-generation boards such as the LPF100A used passive RC filter networks with fixed cutoff frequencies, targeting 50 Hz and 60 Hz industrial power environments. The LPF200A generation introduced improved component tolerances and enhanced EMI shielding, making it compatible with both the S10/2α and S10V backplane form factors. Later revisions addressed thermal derating issues identified in high-ambient-temperature installations common in Middle Eastern refinery environments. As Hitachi transitioned its control platform strategy toward the S10VE and eventually toward open-architecture SCADA integration, the LPF Series entered a maintenance-only lifecycle phase. No direct pin-compatible successor has been released; plants requiring LPF functionality in modernized systems must either retain original hardware or implement equivalent filtering at the field junction box level. This makes original LPF Series boards a critical long-term spare requirement for any facility still operating on HIDIC-based DCS infrastructure.

LPF Series Full Catalog & Functionalities (SKU List)

The following SKUs represent verified components within the Hitachi LPF Series and associated analog signal conditioning range. Each entry reflects a distinct hardware configuration or cutoff specification:

LPF100A: First-generation low pass filter board, fixed RC network, 50/60 Hz dual-rated, S10 backplane compatible.
LPF200A: Second-generation filter board, improved EMI shielding, compatible with S10/2α and S10V backplanes.
LPF200B: Revised LPF200A with updated capacitor specification for extended temperature range operation.
LPF300A: Higher-channel-density filter board, 16-channel analog input filtering, DIN rail mountable variant.
LPF300B: LPF300A with conformal coating for high-humidity environments (offshore and coastal installations).
LPF400A: Active filter variant with adjustable cutoff frequency via onboard DIP switch configuration.
LPF400B: LPF400A with extended input voltage range, supporting ±10 V and 0–10 V signal types.
LPF500A: High-isolation filter board, 1500 V channel-to-channel isolation, for hazardous area signal conditioning.
LPF500B: LPF500A with ATEX-rated component substitutions for Zone 2 classified installations.
LPF600A: Compact 8-channel filter module for space-constrained S10V sub-rack configurations.
LPF700A: Thermocouple-input-optimized filter board with cold junction compensation circuitry integrated.
LPF700B: LPF700A with extended thermocouple type support (K, J, T, E, R, S, B types).
LPF800A: RTD-input filter board, 3-wire and 4-wire Pt100/Pt1000 compatible, with lead resistance compensation.
LPF900A: Strain gauge and load cell signal conditioning filter, bridge excitation voltage integrated.
LPF950A: High-speed filter board for fast-loop control applications, 200 Hz cutoff frequency, S10VE compatible.
LPF-EXT01: External filter termination panel for LPF Series boards, field-wiring marshalling interface.
LPF-EXT02: Extended marshalling panel with surge protection, for LPF Series in lightning-prone installations.

Sourcing Hard-to-Find & Obsolete LPF Series Parts

The Hitachi LPF Series has been in a manufacturer-discontinued status for the majority of its product range. Hitachi Industrial Equipment Systems no longer provides new production units or factory repair services for LPF100A through LPF800A variants. DriveKNMS maintains a dedicated inventory program for obsolete Hitachi control system components, with a focus on the LPF Series boards used in long-lifecycle DCS installations. Our sourcing network covers decommissioned plant equipment, authorized surplus channels, and tested pull inventory from controlled shutdowns. All LPF Series units sourced through DriveKNMS are subject to full functional verification before dispatch. For facilities operating under IEC 61511 functional safety requirements, we provide documentation packages including test records and traceability data upon request. Customers requiring multiple units for critical spare holding programs are encouraged to contact our team directly to discuss volume availability and lead time commitments.

Quality Control for the LPF Series Range

Low pass filter boards present specific verification challenges due to their passive and active analog circuit architectures. DriveKNMS applies a structured test protocol to all LPF Series units prior to shipment. Each board undergoes visual inspection for capacitor bulge, PCB trace corrosion, and connector pin integrity — failure modes common in boards stored in non-climate-controlled environments. Functional testing is performed using calibrated signal generators and precision measurement equipment to verify cutoff frequency accuracy within ±5% of the rated specification. For boards with onboard active components (LPF400A, LPF400B, LPF950A), supply rail voltage regulation and output noise floor measurements are recorded. Backplane connector contact resistance is measured to confirm compatibility with S10 and S10V rack systems. All test data is retained and available for customer review. Units that do not meet specification thresholds are quarantined and not offered for sale.