MIANYANG, SICHUAN, CHINA — April 21, 2026

Industrial instrumentation manufacturer Hammok Tech has released the HM35 differential pressure transmitter, extending the HM-series platform beyond single-line gauge and absolute measurement and into the applications where two process taps matter more than one. The HM35 is aimed at three classes of differential measurement: filter pressure-drop monitoring on OEM filtration and dust-collection skids, flow measurement on orifice-plate and venturi installations, and hydrostatic-level measurement on sealed or pressurized vessels.

The transmitter uses a capacitive silicon-on-sapphire sensor with dual isolating diaphragms, giving it the overrange protection and static-pressure stability that a classic DP cell is expected to carry. Differential range can be specified from 0-1 kPa at the low end up to 0-3 MPa at the high end on a single sensor body — a single hardware platform covers the full differential span that the user would historically have to divide across 2-3 different DP-transmitter product lines.

"For OEM customers, product-line consolidation is one of the real commercial levers we can offer," said the head of product management at Hammok Tech. "A filtration-skid builder does not want to stock five different DP transmitters across their BOM — one for the pre-filter bag pressure, one for the post-filter polish, one for the loop flow, one for the tank level, one for the dosing-pump suction. The HM35 is a single part number across that bill of materials."

Three primary application classes

The first application class is filter-differential monitoring. Bag-filter, cartridge-filter, and dust-collector skids run the pre-filter and post-filter taps into a DP transmitter, which trends the pressure drop across the filter element. When the DP climbs past a configured threshold, the skid triggers a filter-change alarm. The HM35's 0-1 kPa to 0-10 kPa differential ranges, configurable from the HART communicator, cover the great majority of filter-monitoring setups without a hardware change.

The second application class is flow measurement through a primary differential-pressure element — orifice plate, venturi, flow nozzle, Pitot tube, or wedge. These installations measure the square-root of flow as a pressure differential across the primary element, then process the signal either in the transmitter itself (square-root extraction) or downstream in the DCS. The HM35 supports both options: a configurable linear output for DCS-side computation, or an on-transmitter square-root mode for legacy systems that expect a linearized flow signal at the transmitter terminal.

The third application class is hydrostatic level measurement on closed or pressurized vessels. Tank level on an atmospheric vessel can be measured with a single-port gauge transmitter, but once the vessel has a gas head above the liquid, the gas-head pressure biases the single-port reading. A DP transmitter with the low-side tap on the gas head solves the bias problem — the transmitter reads hydrostatic level independent of vessel pressure. The HM35 is tuned for this service with a low-range variant (0-5 kPa to 0-50 kPa) and factory-installed impulse-line fittings compatible with 3-valve and 5-valve manifolds.

Engineers evaluating the HM35 for any of these three application classes can request the full specification datasheet, application notes, and wiring diagrams directly from Hammok Tech.

Sensor and electrical detail

The HM35 uses a capacitive silicon-on-sapphire cell with dual stainless-steel isolating diaphragms and silicone-oil fill on the measurement side. Overrange protection is 4x URL on most variants, which lets the transmitter survive typical process upsets — pump shut-off, valve slam, air-lock — without mechanical damage to the sensor.

Accuracy is ±0.075 % of span on the high-range variants and ±0.1 % of span on the low-range (below 10 kPa) variants. Static-pressure effect is ±0.1 % of URL per 10 MPa of working static. Temperature effect on span is ±0.1 % per 28 °C over the compensated range. These specifications are typical for mid-tier DP-transmitter product lines in the 2025-2026 market and are suitable for custody-transfer-adjacent applications where ±0.1 % performance is the contractual threshold.

Electrical specifications: supply voltage 10.5-36 Vdc, two-wire loop; output 4-20 mA with HART 7 standard; load resistance up to (Us - 10.5) / 0.022 Ohm; burst-mode HART supported; EMC compliance IEC 61326-1; intrinsic-safety option Ex ia IIC T4 (ATEX / IECEx); explosion-proof option Ex d IIC T6.

Process connections include 1/4" NPT (standard on low-range variants), 1/2" NPT, and direct-mount to 3-valve and 5-valve block manifolds. Wetted materials are 316L stainless steel on the baseline variant; Hastelloy C-276 and Monel options are available for chloride and hydrogen-sulfide service.

Why OEM-skid builders care about platform consolidation

The cost argument for HM35 is simple and unglamorous: it reduces the vendor-qualification burden on the OEM customer. Adding a DP transmitter to an approved-vendor list requires electrical-safety review, mechanical integration testing, documentation alignment with the skid builder's ISO 9001 file, and calibration-certificate format validation. Every vendor added to the list carries an annual renewal cost on the purchasing team. A single product line that spans the differential-pressure applications an OEM skid builder runs — filter monitoring, flow, level — collapses that work to one vendor qualification rather than three.

The documentation side also matters. Every HM35 ships with a calibration certificate traceable to national standards, in the same format as the rest of the HM-series catalog. For OEM skid builders who bundle transmitter documentation into the equipment delivery package, a matching-format certificate across every instrument on the skid is a visible quality signal to their end customer.

Commercial availability

The HM35 is available through Hammok Tech's direct sales channel and authorized OEM / EPC partners. Lead time on the baseline variant is 10-14 working days; custom variants (Hastelloy wetted parts, flanged remote seals, extended impulse piping) are 3-4 weeks. Standard commissioning documentation ships with every unit.

About Hammok Tech

Hammok Tech is an industrial instrumentation manufacturer based in Mianyang, Sichuan, China, specializing in pressure and temperature measurement for process-industry applications. Product lines cover general-purpose, industrial, high-temperature, sanitary, corrosion-resistant, differential-pressure, and liquid-level transmitters, alongside RTD and thermocouple temperature transmitters for OEM and plant-instrumentation markets. Full product documentation at https://hammok-tech.com/.