0-100psi liquid pressure sender equivalent to LM34 temp sensor?

[meggin]

Can anyone help me identify a pressure sensor suitable for water pressure duty that is roughly equivalent to Nationals LM34 temperature sensor in terms of cost, linearity, mV output range, and ease of implementation?

Thank you so much.

 

[sreid]

Try Honeywell. The link is to isolated sensors which are more expensive but are usually required for use with water.

http://sensing.honeywell.com/index.cfm/ci_id/16370/la_id/1/type_id/79904.htm

 

[reidh]

I believe MSI sensors has something that may suit your needs.

-Reidh

 

[Comcokid]

Some LM 34 specs:
> Linear +10.0 mV/°F scale factor
> 1.0°F accuracy guaranteed (at +77°F)
> Operates from 5 to 30 volts
> Nonlinearity only ±0.5°F typical
> Cost ~ $0.84 in SOIC and $4.00 in TO-92 at 1000 pieces

The big issue here is cost. What people typically think of as "low cost" does not exist in pressure sensors. Inexpensive pressure sensors run around $20 each in volume.

The lowest cost automotive-type are made by Sensata (formerly the Texas Instruments sensors division). I have priced these in the 2500 piece volumes for a 1 to 5 volt output 250 psi sensor for about $20 to $30 with accuracy and linearity specs similar to what you indicate. This is actually a very good price for a automotive grade fully conditioned pressure sensor ready to screw-in and with built-in connector. Honeywell and MSI make similar type sensors.

http://www.sensata.com/products/sensors/auto-apt.htm

 

[sreid]

Take a look at

Kavlico

Novasensor

 

[meggin]

I think I may have identified something I can work with.
MPX5700GP

http://www.freescale.com/files/sensors/doc/data_sheet/MPX5700.pdf

It's only 14.00 USD and seems to be adequate for very basic pressure monitoring. There is little information about isolation when used for liquid PSI. Any reason why it wouldn't work if used to measure air pressure in a tube connected to the water circuit?

 

[meggin]

Comcokid

I'll contact the folks at that sensata link. Thank you for that. I'll see if they can help me identify what I need. I'm looking at a pretty small volume of these, so twenty to thirty dollars is not out of range at all.

Sealed and threaded would be a very attractive plus.

 

[Comcokid]

Freescale (formerly Motorola) transducer elements like the MPX5700GP (as well as those pressure elements available from others like Fujikura, MSI, etc.) are fine as long as they are used in air. If you look at the datasheet for the MPX5700, you will notice they specifically state "dry air". If you are measuring water, and position the pressure tube such that there is air in front of the transducer, you will have a design that works fine for a few months to a year or two before it fails (been there, done that!-don't repeat my hard-earned lesson!). A sensor element exposed to air in front of water sees moist air, and the sensor element will fail given time. Diaphrams used to isolate only result in hysterisis and offset. Silicon oils injected to cover the element will cause a smaller amount of hysterisis and offset, and only delay slightly the failure from moisture.

Since you posted in an automotive forum, I suggested an automotive grade transducer. There are other manufacturers who make transducers similar in appearance to the Sensata, who also serve the vehicle market (such as Kavlico suggested by sreid). The problem with low volumes is sometimes finding a part that is standard enough that it's available at low volume. Many of the companies servicing vehicles and automotive world only sell in high volume with only a few offerings available otherwise.