CHT-1240 Series: Precision Pressure Sensing with Field Interchangeability
- John Valentini
- Aug 18
- 4 min read
Pressure sensing applications in medical equipment, life science instrumentation and unmanned aerial vehicles often share a common requirement: small pressure changes must be measured accurately even as operating conditions change. In these systems, room-temperature accuracy alone does not define sensor performance. Thermal stability, repeatability and the ability to replace one sensor with another without extensive system recalibration can be equally important.
The AV Sensors CHT-1240 Series combines high pressure accuracy and low thermal errors with a constant-voltage excitation architecture designed to provide 1% field interchangeability. It also provides OEMs with a replacement option for legacy TE Connectivity 1240 Series pressure sensors.
Constant-Voltage Operation with Field Interchangeability
One of the important characteristics of the CHT-1240 is its approach to sensor excitation and interchangeability.
Unlike the CHT-1230 Series, which is designed around a constant-current excitation approach, the CHT-1240 is intended for operation from a constant-voltage application circuit. An integrated current-set resistor is incorporated into the sensor and used by the recommended external circuit to establish the appropriate excitation for the individual pressure sensor.
This architecture addresses an important characteristic of piezoresistive pressure sensors: individual sensor bridge resistance and sensitivity can vary from device to device.
With the CHT-1240, the current-set resistor provides information specific to the individual sensor. When incorporated into the recommended application circuit, it adjusts the sensor excitation so that variations between devices are substantially reduced. AV Sensors specifies 1% field interchangeability when the CHT-1240 is used with the recommended application circuit.
For an OEM, this can provide an important system-level advantage. A replacement sensor can be installed without requiring the degree of individual calibration that would otherwise be necessary to compensate for sensor-to-sensor sensitivity variation.
Accuracy That Extends Beyond Room Temperature
Field interchangeability addresses variation between sensors. Thermal compensation addresses another source of measurement uncertainty: variation within the same sensor as temperature changes.
The CHT-1240 provides a −20°C to +70°C compensated temperature range and low thermal errors for both offset and span.
Key performance characteristics include:
0.1% FSS typical pressure non-linearity
±0.5% FSS maximum thermal error of span
±0.5% FSS maximum thermal error of offset
±0.05% FSS typical temperature hysteresis of offset and span
±0.1% FSS long-term stability of offset and span
100 µs response time
−40°C to +125°C operating temperature range
The result is a pressure sensor platform designed to control several different sources of measurement error: linearity, temperature effects, long-term stability and device-to-device variation.
Medical Ventilators and Respiratory Equipment
Life science equipment frequently uses pressure measurement to monitor pneumatic circuits, pumps, filters, flow paths and process conditions. These systems may operate continuously for extended periods, making both short-term accuracy and long-term stability important.
The CHT-1240 combines a rugged ceramic hybrid construction with ±0.1% FSS specified long-term stability of offset and span. Multiple pressure ranges and absolute, gauge and differential configurations allow equipment designers to use the same sensor family for different measurement functions.
The combination of thermal stability and 1% field interchangeability is particularly useful for instrumentation manufacturers seeking predictable performance across production quantities rather than simply optimizing the performance of an individually calibrated prototype.
UAV Airspeed and Altitude Measurement
Pressure sensing plays a fundamental role in UAV flight systems, particularly for airspeed, altitude and barometric pressure measurement. Unlike laboratory instrumentation, UAV pressure sensors may encounter significant temperature changes during operation.
The CHT-1240 combines high pressure accuracy, low thermal errors and fast response in a compact PCB-mounted package. Differential configurations can be applied to airspeed measurement, while absolute pressure configurations support altitude and barometric pressure measurements.
The constant-voltage architecture and current-set resistor also provide OEMs with a controlled method of achieving consistent sensor performance from unit to unit—an important consideration when the same electronics are produced across multiple aircraft.
A Practical TE 1240 Replacement Path
For manufacturers maintaining equipment originally designed around the TE Connectivity 1240 Series, component availability can create a problem considerably larger than the cost of the pressure sensor itself. Changing the sensor architecture may require PCB redesign, changes to signal conditioning, documentation updates and product requalification.
The AV Sensors CHT-1240 provides a replacement path that preserves the dual-in-line PCB package and constant-voltage/current-set-resistor approach associated with this sensor architecture.
That distinction is important. The CHT-1240 should not be viewed simply as another mV-output pressure sensor that can be electrically substituted into an existing system. The application circuit and integrated current-set resistor are part of the overall sensor solution, providing the specified 1% field interchangeability.
More Than a Legacy Replacement
The ability to support existing TE 1240 applications is valuable, but it should not define the CHT-1240.
For a new design, its combination of high accuracy, low thermal errors, 1% field interchangeability, fast response and flexible pneumatic configurations provides a strong foundation for precision pressure measurement.
For medical ventilators, life science instrumentation and UAV systems in particular, the CHT-1240 addresses three different design objectives simultaneously: maintaining accuracy as temperature changes, achieving consistent performance from sensor to sensor, and simplifying integration into OEM electronics.
For an existing TE 1240 design, that provides a practical replacement strategy. For a new application, it provides something broader: a thermally stable, field-interchangeable pressure sensing platform designed around predictable system-level performance.
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John Valentini, Business Development AV Sensors (business.development@avsensors.com)
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