Differential Pressure Transmitters

Differential pressure transmitters measure the pressure difference between two points and convert it into a signal HVAC systems can act on. They govern airflow through ducts, detect when filters need changing, maintain the pressure differentials that separate critical spaces from adjacent areas, and feed the control logic that keeps buildings comfortable and code-compliant. A DPT that reads accurately is invisible. One that drifts, lags, or loses calibration becomes the source of problems that are difficult to trace and expensive to fix.

The pressure differences that HVAC DPTs measure are often very small, sometimes in the tens of pascals. At those levels, noise from fans, blowers, and AC-powered equipment becomes a real problem, as do thermal sensitivity and long-term drift. A sensor that performs well in a controlled lab environment may not maintain its accuracy once installed in a mechanical room with variable temperatures, vibration, and electrical interference. These factors compound over time, and the result is a transmitter that was accurate at commissioning but cannot be trusted a year later.

The HV Series was built to meet these demands directly. Built on the NimbleSense architecture, it delivers the accuracy, noise rejection, and long-term stability that low-range HVAC differential pressure measurement requires, with digital filtering designed for the fan and blower noise environment of commercial HVAC systems, long-term stability specified in pascals rather than as a percentage of full scale, and multi-range flexibility that allows a single device to cover the full span of HVAC pressure applications.

Why Choose Superior Sensor for Your DPT

DPT performance is determined at the sensor level, before any signal reaches the system. Superior Sensor Technology’s NimbleSense architecture delivers measurement accuracy and noise rejection tailored to the low-pressure, high-interference environments where HVAC DPTs operate.

Recommended Sensors

Common Device Features: 3.3V supply
Long-Term Stability is measured after first 12 months
Short-Term Error Band (STEB) is measured over 24 hours, after auto-zero

Common Specifications

Differential Pressure Transmitter (DPT) FAQ

What is a differential pressure transmitter and how does it work?

A differential pressure transmitter measures the pressure difference between two points in a system and converts it into an electrical signal that control systems can interpret and act on. In HVAC applications, DPTs measure the pressure difference across filters, duct sections, coils, and fans to infer airflow, detect restrictions, and maintain system balance. The transmitter’s accuracy determines the accuracy of every downstream control decision.

What pressure ranges are typical for HVAC differential pressure transmitters?

HVAC applications span a wide range. Filter monitoring typically operates at 25 to 250 pascals. Duct static pressure typically ranges from 50 Pa to 1,000 Pa or more, depending on the system design. Room pressurization for isolation or cleanroom applications may operate at 5 to 50 Pa. Because these ranges vary significantly within a single building, DPTs with multi-range capability offer a meaningful design and inventory advantage over single-range devices.

What causes drift or inaccuracy in differential pressure transmitters over time?

The primary causes are thermal effects, mechanical stress, and sensor aging. Temperature changes cause sensor materials to expand and contract, shifting the zero point and span. Vibration from nearby mechanical equipment accelerates mechanical fatigue. Power-line interference from motors and variable frequency drives introduces electrical noise that appears as measurement error. In low-pressure HVAC applications, where the signals are already small, these effects have an outsized impact on reading accuracy.

How does the AZ100 auto-zero valve work with the HV Series in permanently installed DPT applications?

Zero-point drift in a differential pressure sensor accumulates gradually as the sensor’s baseline shifts due to thermal cycling, element aging, and environmental variation. In permanently installed HVAC DPTs that run continuously, common in commercial and institutional buildings with year‑round climate control, drift that builds up between commissioning and the next service visit can degrade accuracy enough to compromise filter loading thresholds, VAV set points, and pressure alarms. The AZ100 auto‑zero valve addresses this by automatically exposing both pressure ports of the HV Series sensor to the same reference pressure at configurable intervals, measuring any deviation from zero and correcting it without a technician visit or system shutdown. In climates with long heating seasons, where systems may operate for months between service windows, the AZ100 helps maintain zero accuracy throughout the operating period so the DPT holds its commissioning performance and keeps filter monitoring and pressure differential controls reliable from the first week of the season through the last.

How does multi-range capability benefit DPT product design?

A DPT with multi-range capability can cover several measurement ranges within a single hardware design, rather than requiring separate sensor variants for each application. For a manufacturer building DPT products for multiple HVAC applications, this reduces the SKU count, simplifies inventory management, and enables a single certified design to serve a broader market. It also allows range changes in the field without hardware modifications, which is valuable in installations where system conditions change over time.