When automobile doors are closed it is expected that the sealing surfaces around the edges of the door will contact the frame properly so that the passenger cabin is weatherproof and the inside protected from rain and water. With all the different styles of doors, frames and gasket materials each new model must be tested to verify that the sealing system is effective.
One way to test the seal is to measure the pressure rise inside the passenger cabin when the door is slammed shut. If the seal is effective there will be a brief rise in pressure. We have probably all experienced this – Volkswagen Beetles were notorious for the ear discomfort on door closings as they were deigned to be waterproof. So a balance between sealing effectiveness and comfort is desired and testing the pressure rise is one way to verify that the right combination of sealing materials is being used.
The measurement of a pressure rise in the passenger cabin requires a pressure transducer with sensitivity to low pressures and fast dynamic response. One automobile manufacturer uses the Validyne DP45 to measure pressure spikes on the order of 400 Pa having a duration of 10 mSec. The DP45 is available in full scale ranges as low as 220 Pa and has a flat dynamic response on the order of 60 Hz and can thus capture a transient whose rise time is 4 mSec.
The system is comprised of the following Validyne Parts:
- DP45-18-A-1-S-4-D Pressure Sensor
- CD16-A-1-A Carrier Demodulator
- 1280-1002 Mating Electrical Connector
- Cal-B2 – System Calibration for 0 to 400 Pa = 0 to +5 Vdc
The system cal is convenient because of the low pressures involved – we calibrate the system here prior to shipment. The customer attaches DC power (9 to 55 Vdc) to the connector and also the 0 to +5 Vdc signal wires to a high speed data acquisition system. The transducer has 1/8” female NPT ports and these are fitted with adapters by the customer to plastic tubing that is run to the inside of the automobile passenger cabin. The door is slammed several times at various velocities and the resultant pressure rises recorded. On this basis the gasket seal and firmness can be evaluated.