It never fails, when you really need a board level pressure sensor, the device you require is not in stock. In order to work around this, there are options to get past the exact part you require, without having to re-qualify another device especially, if you only need a few pieces to get by. There are always a few options available some are better than others, but each application is different. This blog will outline only a few possible ideas which engineers (and purchasing agents!) should consider if the primary board level pressure sensor is not readily available. (These are in no particular order.)
Pressure Sensors – Devices with a Millivolt output
Board level products are usual the easiest part to find a part close to what was originally desired. There are a few options to consider:
1) Pressure References
One of the easiest substations is to think about the pressure reference utilized: Gauge, differential or absolute. In many cases, the device specified into a design is a gauge part. A possible substation is to use a differential device instead of a gauge. Also, many applications an engineer has specified differential, but in reality a negative pressure is not really seen in day to day operations. A gage reference instead of a differential may be an option.
If an absolute device was specified, there is no option in switching to a gauge of a differential device. The only substitute for an absolute device is another absolute device.
2) Pressure Units
Few people think of this option, but sometimes a manufacturer may have devices which were calibrated in other pressure units like, bar, mmHg etc, instead of psi. Most manufacturers make life pretty simply for themselves by using the same pressure, but just changing the units. For instance, many manufacturers offer a device in bar. One bar equals 14.5 psi. The manufacturer will use a 15 psi device, but calibrate the device to 14.5 psi. There are lots of websites which show the calibration in various units. Here are a couple which we use with some regularity: www.digitaldutch.com/unitconverter or www.chemie.fu-berlin.de/chemistry/general/units.
3) Pin configuration
This is the ugliest of all of the solutions and sometimes not a realistic option. Many board level pressure sensors families offer pins straight up or straight down compared to the pressure ports. Most design us a pin configuration which point down. In a pinch, the vertical pins can be manually turned down. You do not get to “wiggle” the pins too much as they will break off.
Also, a word of caution, using this type of substation will void any warranty. You will own the parts if you take this type of substitution.
4) Pressure ranges
This is always the easiest substation. If you need a specific pressure range, an easy substation to consider using is the pressure range higher to lower than the one required. However, please be aware that the electric circuit might need to be adjusted to make this work. (This is due to the sensitivity change.) Substituting a high pressure range will result in a lower sensitivity than required. Conversely, if a lower range is substituted, the sensitivity will be too high.
This can be worked around by adjusting the power supply, or gain resistors, but this solution will require some tuning to get the required sensitivity. While this is an easy change, additional steps will be required to make this option work.
5) Another vendor:
The pressure sensors community, from a manufacturers stand point, is a small gene pool. (The author has worked for 5 vendors.) In all most all cases, it is not uncommon for two (or more) vendors to manufacturers the same device. Be sure to ask for this option, as some parts are a form, fit and function drop in for another manufacturer device.
6) Package Configurations:
The final option is, what many would compare with a going nuclear, and should really only be used when nothing will work, “looks don’t count”, and only a few pieces are require. Ask to speak with an application engineer and select another type of device other than the one you require, that has the most important quality to you. For instance your design requires a ten inch of water sensor and you require a TO-8 housing. For a few pcs another board level device may get you through the pinch.
Let’s hope you never end up in this situation.