Differential Pressure Transmitter

Selecting a differential pressure transmitter requires comprehensive consideration of multiple factors, including measurement range, 

overload capacity, response speed, output signal, and environmental adaptability. Based on your provided operating conditions: 

the upstream pump is connected to an atmospheric pressure pipeline; the upstream negative pressure reaches 0.5 MPa when not 

running, and the maximum pressure after pump startup is 1.1 MPa, exhibiting significant pressure fluctuations; the data acquisition

 frequency requirement is 10Hz (some systems support 50Hz); the output signal is a standard 4-20mA; and the operating temperature

 is ambient temperature—the following are targeted selection suggestions.

I. Core Parameter Analysis and Selection Basis

Differential Pressure Range Calculation

Since the downstream pressure is atmospheric (considered 0 MPa), and the upstream pressure varies between -0.5 MPa (negative pressure) 

and +1.1 MPa, the total pressure range the transmitter must withstand is:

1.1 − (−0.5) = 1.6 MPa

Considering pressure fluctuations and instantaneous peak values, it is recommended to select a transmitter with a range slightly greater

 than 1.6 MPa. To ensure accuracy and stability, it is generally recommended that the operating pressure be within 1/4 to 3/4 of the range. 

Therefore, differential pressure transmitters with ranges of 0–3.5 MPa or -1.75–+1.75 MPa are recommended, as they fully cover the actual

 pressure variation range and provide a safety margin.

Overload and Burst Pressure Requirements: Instantaneous impact pressure may occur during pump startup. It is recommended that the

 maximum operating pressure of the selected transmitter be at least 1.5 times the full scale, and the burst pressure should be even higher.

 For example, if a 3.5 MPa range is selected, the maximum operating pressure should be ≥5.25 MPa, and the burst pressure ≥7 MPa to

 ensure long-term operational reliability.

Response Frequency Matching: The sampling frequency requirement is 10 Hz (i.e., 10 samples per second), meaning the transmitter

 response time should be ≤100 ms. Some high-performance differential pressure transmitters can have response times as low as below

 20 ms, such as products using diffused silicon or capacitive sensors. Models with a response time ≤50 ms are recommended to meet 

dynamic pressure monitoring requirements. Output Signal Standard: The output is a standard 4-20mA DC two-wire signal, suitable for 

most PLC and DCS control systems. This signal has strong anti-interference capabilities, is suitable for long-distance transmission, and 

features a disconnection detection function (0mA indicates a fault).

Power Supply and Load Capacity: The typical power supply voltage is 24V DC (allowable range 10-32V DC). The power supply capacity

 and line voltage drop of the control system must be confirmed. The transmitter load resistance generally needs to meet the following

 requirements:

For example, with a 24V power supply and a minimum transmitter operating voltage of 10V, the maximum load resistance is 700Ω.

 Ensure that the total circuit impedance (including cable resistance, input impedance of the acquisition module, etc.) does not exceed 

this value.

Installation and Protection Requirements: It is recommended to select products with an IP65 or higher protection rating to prevent 

dust and moisture intrusion. Electrical connections should use M12 or Hirschmann connectors to improve reliability. If vibration is 

present in the field, a model with strong vibration resistance should be selected.

II. Reasonableness Analysis of Recommended Model: CX-PT-1151A-3.5MPa

Your recommended model, CX-PT-1151A-3.5MPa, meets several key indicators:

**Measuring Range Matching:** The 3.5MPa measuring range fully covers pressure variations from -0.5MPa to +1.1MPa, and the 

operating point is located in the middle of the range, which is beneficial for improving measurement accuracy and extending service life.

**Technical Basis:** This series is based on the capacitive sensing principle (similar to the 1151 model), featuring simple structure,

 high accuracy, good stability, and strong overload capacity.

**Output Compatibility:** Standard 4-20mA output, compatible with mainstream control systems.

**Response Capability:** Typical response time ≤200ms, some improved models can reach within 50ms, basically meeting the

 10Hz sampling requirements.

**Environmental Adaptability:** Operating temperature -20～85℃, suitable for normal temperature conditions; protection rating up

 to IP67.

Conclusion: Under the premise of no stronger impact or higher frequency dynamic requirements, CX-PT-1151A-3.5MPa is a reasonable

 and safe choice.

Email:sales01@cxflowmeter.com

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