Designed for OEM applications
By using a differential pressure sensor or transducer, an operator can confidently know when a filter change is required by monitoring the output signal.
Differential Pressure Transducer Definition
Differential pressure sensors and transducers measure the difference in pressure between two points, typically referred to as P1 and P2 or high side and low side. A differential pressure transducer is a great choice for continuously monitoring the condition of a filter within a system. By using a differential pressure transducer, an operator has a live view, via the pressure transducers’ output signal, of the condition of the filter. This eliminates the need to repeatedly shut down the system for inspection or routinely change filters when maintenance is not required. Using a differential pressure transducer is recommended over two individual pressure transducers because it eliminates potential compounded inaccuracies and the need to calculate the difference between two transducers.
Types of Liquids and Gases
- Air
- Fuel / Fuel oil / Diesel fuel
- Oil
- Water
- Refrigerant / Glycol
- Natural gas
Differential Filter Applications
- Diesel Particulate Filter (DPF) monitoring
- Catalytic converter monitoring
- Commercial water filtration systems
- HVAC chillers
- Gloveboxes
- Engines
- Marine FO systems
The Measurement Process
- Upstream pressure, or line pressure, flows to the filter installed in the system. A pipe is installed pre-filter which allows for the upstream pressure to flow to P1, or the high side, of the differential pressure transducer.
- Media flows through the filter and any contaminants are removed.
- The downstream pressure (post filter) continues to flow through the system. A pipe is installed post filter which allows for the downstream pressure to flow to P2, or the low side, of the differential pressure transducer.
- The filter will become clogged over time as contaminants are removed. This will cause the downstream pressure to decrease, creating an increase in differential between P1 and P2. As the differential increases, the linear output signal of the transducer will increase.
Real World Example
Fuel Filter monitoring
A customer has a diesel generator and is looking to monitor the condition of the fuel filter. The line pressure of the application is 80 PSI and the customer would like to replace the filter when the downstream pressure reaches 50 PSI, a 30 PSI differential. We would recommend our CS14 Differential Pressure Transducer with a 4-20mA output signal and a calibrated differential range of 30 PSI.
When a new filter is installed and the generator is started, the pressure transducer will read 4mA (figure 1 below) as there is no differential between P1 and P2. As the filter removes contaminants and starts to become clogged, the output signal of the pressure transducer will increase because the downstream pressure is less than the upstream. In this application, the pressure transducers output signal will be 12mA when the downstream pressure falls to 65 PSI, a 15 PSI differential (figure 2 below). This will signify that half of the filter’s life is left. Eventually, as the filter continues to remove contaminants and become more clogged, the output signal of the transducer will reach 20mA (figure 3 below), signaling to the operator that 30 PSI of differential has been reached and it is time to change the filter.
Figure 1
Figure 2
Figure 3
Why not just use two separate pressure transducers?
A common question that comes up when working on filter monitoring applications is
“Can I just use two separate pressure transducers to measure the pressure differential?”
The answer is yes, two separate pressure transducers can be used to measure the differential pressure of a filter application. However, there are some potential issues that first need to be considered.
Compounded inaccuracies
If you are using two pressure transducers, each with a ± 0.5% accuracy, your potential inaccuracy is doubled to ± 1%. If you were to instead use the CS14 Differential Pressure Transducer, you would only need to consider the accuracy of the single transducer, in this case ± 0.25% BFSL (± 0.5% for 2 PSI & below). Also, while we temperature condition every sensor during the manufacturing process, it is possible for each transducer to behave differently in varying temperature conditions. For example, if the ambient temperature of the application goes from room temperature to 55°C, the upstream transducer could have a TC Span error of -0.5% while the downstream transducer has a TC Span error of +0.5%. Using a dedicated differential pressure transducer would eliminate this compounded inaccuracy potential.
Potential user error
When two single pressure transducers are used, customers will need to create a program or manually calculate the difference in readings from the upstream and downstream transducer. This introduces the potential for a mistake to be made which, if not caught early, could result in damage to equipment due to lack of flow in the system post filter or contamination of the system’s media due to a overly clogged filter. Our differential pressure transducers automatically calculate the difference in pressure from P1 to P2 and transmit a linear output signal to your PLC or control panel.
Recommended DP Sensors for Filter Condition Monitoring
Designed for OEM and Hazardous locations
Frequently Asked Questions
What is a wet/wet differential pressure transducer?
A wet/wet differential pressure transducer is a type of differential pressure transducer that can measure the pressure of liquids and gases. This differs from a dry/dry transducer, which is limited to pneumatic applications. Even in certain gas applications, moisture can build up within the system to limit the survivability of the sensor. Wet/wet differential pressure transducers provide greater compatibility and survivability.
Core Sensors’ differential pressure transducers can be used to measure liquids and gases or pneumatic applications. Contact the factory to discuss your liquid or gas and media compatibility. Custom differential pressure transducers are possible.
What are the key components of a differential pressure transducer or transmitter?
A differential pressure transmitter typically consists of:
- A pressure-sensing element (often a diaphragm with a strain gauge, differential capacitance, or vibrating wire sensor). Core Sensors employs two stainless steel diaphragms within the same sensing element to measure differential pressure between both sides.
- Two pressure ports labeled as “High” and “Low”.
- Electronics housed separately to process the signal. Core Sensors uses the specialized ASIC technology to calibrate the output signal specific to the sensor’s operation over pressure and temperature.
How low of a differential pressure range can you offer?
Our standard differential pressure range minimum pressure is about 0.5 PSID or 14″ water column differential. For lower pressures, contact the factory to discuss the application and if a lower pressure can match the application conditions.
What is bi-directional measurement?
In a bi-directional differential pressure transducer, the output signal midpoint is set to 0 PSID and the measurement range is equal on either side of the mid-point. For example, a bi-directional differential pressure transducer can have a +/- 5PSID measurement range with a 4-20mA output signal. -5 PSID would be set to 4mA, 0 PSID would be 12mA, and +5 PSID would be 20mA. This is common for applications that have bi-drectional flow of liquids or gases or when a system incurs a vacuum pressure that requires the measurement to be read to ensure the system has been fully evacuated.
For filtration applications, a pressure flow might shift to the opposite direction to purge the filter.
What are the common output signals of differential pressure transducers?
The output signals from industrial differential pressure transducers are typically 4-20mA or voltage outputs. 4-20mA DP transmitters are simple two-wire, loop powered units which can transmit long distances. Voltage outputs typically have shorter distances, yet offer greater flexibility for low power/current consumption applications such as remote telemetry.
Are custom differential pressure transducers available?
For OEM applications, Core can customize our differential sensor platform to meet your needs. From process connections and electrical connections to materials and outputs, Core will partner with you to design and manufacture the right product. Note that for hazardous area rated products, the level of customization can be extended based on additional testing requirements and resubmission to approval agencies.
For more information: custom differential pressure transducers
What’s the difference between your hazardous location models?
| Product Series | Approval | Electrical Connection Options |
|---|---|---|
| CS14 Wet/Wet Differential Pressure Transducer | Standard OEM design | Cable, Connectors, Conduit with cable |
| CS54 Non-Incendive Differential Pressure Transducer | Class I Division 2 Groups A, B, C, D | Conduit with cable, DIN 43650 A, Minifast |
| CS64 Explosion-proof Differential Pressure Transducer | Class I Division 1 Explosion-proof Groups A, B, C, D | Conduit with wire leads |
| CS84 Intrinsically Safe Differential Pressure Transducer | Class I Division 1 Intrinsically Safe Groups C, D | Cable, Connectors, Conduit with cable |
Connect With Our Sales Team
Have questions about differential pressure transducers or choosing between our products? Need a quote? We are ready to help! Fill out the form and a member of our sales team will contact you to discuss your requirements. You can also give us a call at (862) 245-2673.
