---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 03/21/24: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:46 PM - Instrumentation amplifiers (Finn Lassen) ________________________________ Message 1 _____________________________________ Time: 05:46:26 PM PST US From: Finn Lassen Subject: AeroElectric-List: Instrumentation amplifiers Trying to measure pressure in front of my radiators to somehow get uniform airflow through entire rad surface. A few years ago I bought 5 MPX10DP 10kPa (1.45psi) pressure sensors because they were relatively inexpensive. Been measuring 1" from each corner and center. But have now added steering vanes in # pattern -- in other words rad surface now divided into 9 squares. Throwing good money after bad I just ordered additional 4 MPX10DPs. Problem with the MPX10 sensors is they are not amplified (nor temperature compensated). Only outputs 35mV/10kPa. However outputs are offset at about 2.5V when fed 5V. Basically wheatstone bridge. The smarter move would have been using MPX5010DP sensors. They are internally amplified and temperature compensated. Output between 0.5 and 4.5V. However they are considerably more expensive. I've been using two of LM324 opamps for each sensor to handle offset and get the amplification I'd like. Had not looked at temperature compensation because mainly interested in relative pressures over the 5 channels. Not expecting to see more than 20 inH2O or 5 kPa so 250x amplification would be ideal but at least 140x to get full range from the MPX10DPs. Now I've seen mention of INA122 (about $5+ each) and similar instrumentation amplifiers which are designed for the MPX10DP type of sensors. Came across the INA350CDS instrument amplifier reasonably priced at less than $1 at Mouser. However only 50x amplification. Thinking of making a PCB for the 9 MPX10DPs and amps. Before I do I'm wondering if any of you have experience in this area (differential input instrument amplifiers with output going to 0-5V input A/D converters) and may have other suggestions. Inexpensive differential input instrument amplifiers with digital outputs? Or some other modern ICs I'm not aware of. Finn P.S. I did consider 3D printing a 9 to 1 valve to be driven by a stepper motor and just one MPX5010DP pressure sensor but worried about how long it would take for pressure to settle out after changing from one input to the next. Currently logging the 5 channels 2 times per second but able to log much faster. ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.