Blog Alrededor How to select the 26PCAFA6D pressure sensor and its medical applications?

I . How to select the 26PCAFA6D pressure sensor and its medical applications?

26PCAFA6D is a low-pressure differential pressure sensor in the Honeywell 26PC series, with notable applications in medical respiratory equipment, lung capacity measurement devices, airflow monitoring equipment, and pressure detection modules in medical instruments.

The key selection criteria for this product are: whether the pressure range matches, whether the differential pressure measurement method is correct, whether the output signal can be read by the main control circuit, and whether the sensor meets the material and safety requirements of medical equipment.

Below is an analysis from three aspects: product technical parameters, selection methods, and medical applications.

Basic Product Information
Project parameters
Brand :  Honeywell
Series : 26PC
Model : 26PCAFA6D
Product Type : Onboard Differential Pressure Sensor
Measurement type : Differential pressure
Nominal pressure range : ± 1 psi (approximately ± 6.89 kPa)
Output type : Wheatstone Bridge
Full scale output : of approximately 16.7 mV (when powered by 10V)
Power supply voltage  : typical 10V, product specification range needs to be checked
Accuracy of approximately : ± 0.5%
Response time : approximately 1 ms
Installation method : PCB through-hole installation
Encapsulation : 4-SIP
Interface : Dual pressure interface
Working temperature : -40~85 ℃

Special attention should be paid to:

1. This is an unenhanced millivolt level output sensor, not a sensor that directly outputs 0-5V or 4-20mA.
2. ± 1 psi is the differential pressure measurement range, not the normal absolute pressure measurement range.
3. Its dual ports are connected to P1 and P2 respectively, and the pressure difference between the two ports is used for measurement.
4. External amplification and signal conditioning circuits are required to easily connect to ordinary MCUs or ADCs.

II .  How should 26PCAFA6D be selected?
I suggest following the following six steps to make a judgment.
1. Select based on pressure range
This is the most important parameter.

The 26PC series has different pressure levels:

Model                  pressure range                                typical application directions
26PCAFA6D        ± 1 psi                                              lung capacity and low-pressure airflow detection
26PCBFA6D        ± 5                                                   psi medium and low pressure difference detection
26PCCFA6D        ± 15 psi                                           high pressure difference detection
26PCDFA6G       30 psi                                              gauge pressure detection
26PCFFA6G      100 psi                                             high gauge pressure detection

Selection principle:

-Measure small pressure changes: prioritize low range models.
-Measure the pressure difference generated by respiratory airflow: focus on evaluating 26PCAFA6D.
-Measuring higher pressure: Models with larger ranges need to be considered.
-If the actual pressure often exceeds the range, even if it does not reach the breaking pressure, it does not mean that the measurement is accurate.

Note: The larger the range, the better the product. For small pressure changes, excessive measurement range can reduce effective measurement resolution.

 Select based on pressure type

We need to first clarify which type of pressure the equipment is measuring.

Meaning and applicability of pressure types
Pressure difference between two positions, respiratory airflow, filter pressure difference
Pressure pump and pipeline pressure relative to atmospheric pressure
Absolute pressure relative to absolute vacuum pressure vacuum system, absolute pressure monitoring

26PCAFA6D is a differential pressure type.

For example, in a lung capacity measurement device:

-P1 is connected to one side of the airflow channel.
-Connect P2 to the other side of the airflow channel.
-When gas passes through a flow resistance element, a pressure difference is generated.
-The sensor converts the pressure difference into an electrical signal.
-The main control system calculates the airflow velocity and flow rate based on the calibration relationship.

1. Select based on the output signal

The 26PCAFA6D uses a Wheatstone bridge output, with a typical full-scale output of approximately 16.7mV (10V power supply).

This means:
-The motherboard needs to support millivolt level differential signal acquisition.
-Usually requires instrumentation amplifiers or high-precision amplification circuits.
-ADC needs to have sufficient resolution.
-Temperature compensation, zero calibration, and power stability need to be considered.
If the customer's device can only receive 0-5V signals and cannot directly connect this sensor to the motherboard, a signal conditioning circuit needs to be added.

2. Selection based on gas medium

The material compatibility of 26PCAFA6D needs to be carefully checked.

Especially medical equipment:
-Do you come into contact with moist exhaled gas?
-Is there condensation water present?
-Do you need to come into contact with oxygen?
-Is there contact with disinfectants or cleaning agents?
-Is there a risk of biological contamination?
The original factory data has material compatibility limitations for the contact medium and cannot be assumed to be applicable to all medical gases or liquids.
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3. Select based on installation method

Need to confirm:
-Is it encapsulated with 4-SIP?
-Is the PCB pin position consistent?
-Are the directions of P1 and P2 air ports matched?
-Does the diameter of the trachea match?
-Is there any air leakage after installation?
If replacing old equipment, it is recommended to directly compare the complete model, pin diagram, air port position, and electrical parameters of the original sensor, rather than just comparing the pressure range.

4. Select based on the work environment

Attention should also be paid to temperature, humidity, vibration, and pressure shock.

The compensation temperature range of the 26PC series is usually 0-50 ℃, and the working temperature range is not the same as the compensation temperature range. For medical respiratory equipment, it is particularly important to verify the long-term stability of exhaled gas in high humidity environments.

III. What are the applications of 26PCAFA6D in the medical field?
The medical application of this product has a clear technical basis.

1. Spirometer:
There are original factory application cases
Measure the small differential pressure generated during the patient's exhalation or inhalation process to assist in calculating airflow velocity, respiratory flow rate, and lung capacity.

2. Hemodialysis equipment:

Used for pressure monitoring of related fluid circuits, helping equipment monitor the pressure status during the filtration process. The location for differential pressure measurement needs to be determined based on the actual equipment structure.

3. Ventilator and respiratory circuit monitoring:

It can be evaluated for air flow differential pressure monitoring, assisting in flow calculation or determining air path changes, but the range, air path design, and dynamic response requirements must be verified.

4. Medical air filtration equipment:

It can be evaluated for monitoring the pressure difference before and after the filter, helping to determine changes in filter resistance and blockage trends.

IIII. A real application case worth paying attention to: spirometer

Honeywell Original Factory Success Stories

Honeywell has released a successful case study in the medical industry, introducing the application of 26PCAFA6D in handheld lung capacity measurement devices in China.
leytemed.en.made-in-china.com

Customer Requirements:

A customer who produces handheld spirometers needs to measure the airflow during the user's exhalation process to calculate lung capacity for health and fitness analysis.
But the customer encountered a technical issue:
The exhaled gas has a high humidity, and the sensor must be able to work stably in a high humidity environment.
Solution:

The customer uses Honeywell 26PC onboard pressure sensor, specifically model 26PCAFA6D.
Using sensors to measure the differential pressure generated by respiratory airflow, and then calculating respiratory flow and lung capacity through device circuits and algorithms.
Application value:

1. Meet the measurement requirements for small pressure differences.
2. Support miniaturization design for handheld devices.
3. Use differential pressure measurement to achieve respiratory airflow detection.
4. Provide pressure signals required for respiratory data calculation to the device.
Case Business Achievements:

Honeywell's original factory case revealed that the corresponding annual business amount for this application is approximately $90000.
Newark Electronics

Original case reference: Honeywell Medical Success Stories PDF.

It should be noted that this case demonstrates the practical application of this model in lung capacity measurement equipment, but it does not mean that all medical devices can be directly used, nor does it mean that the sensor itself has obtained medical device certification.