Electrostatic Discharge Protection

Most functioning electronic devices are immune from ESD damage.

It's the unconnected components, mostly CMOS and other ESD sensitive devices that must be kept at a neutral potential with their surroundings.

If, this is a requirement of some customer or just your company management, you may be better off going with a know ESD protected system.

Managers have no common sense and seeing a wire running from the sensor to a water pipe may not convince them the device is protected.

People wear ground straps and work at grounded benches when assembling ESD sensitive devices.

More info on the type of devices and the operating environment would be helpful.

Thanks everyone,

You guys are absolutely right. The operating environment is going to be very rugged (for farming). Since we are in Canada, we might need to operate it under very cold weather.

Regarding the sensors, we are searching for those ready-to-use industrial devices just for now. If my boss thinks that the prices are too high, we might need to make our own PCB board. So far, I am on the job of searching for an inclinometer. I have find a bunch of them that fits my requirement. However, for a single axis, -/+45 degrees of measurement, 24 Vdc power input, and analog output (voltage readings), I am not too sure how much would it cost.

I'm confused.

You want an analog output. Where will the display be? In dash?

What is the total requirement?

This:

is what pilots use.

Cool stuff! The analog output can be either voltage readings, eg. 0V to 5V, or current readings like 4 mA to 20 mA. All of these signals will be transmitted by a microcontroller through wifi, and then be displayed in digital on a Android tablet. The tilt sensor needs to be programmed to have a feature of self-levelling.

The OP should tell us more about the intended sensors. And like lyn said, it's mostly a concern when it comes to unconnected devices, i.e. storage and, mostly, handling issues.

Once the device or component connected, ESD should be less a problem, depending on the situation it will be more about EMC as in most cases you can ground metal cases, metal connectors, cables shields,... properly enough to prevent ESC problems.

About ESD it's important to remember that ESD damages do not necessarily destroy a component, they can also lead to a more or less dramatic life shortening, so it's not always possible to immediately assess ESD damages as they may appear only later, sometimes years later.

Are you referrring to MEMS inclinometers? High end modules with integrated microcontrollers or basic ones for general purpose uses?

Which types of temperature sensors?

Do you mean sensors as bare OEM electronic components or ready-to-use industrial devices?

When it comes to sensors you can find about everything, it's mostly a question of money (like inclinometers down to 1 micrometer per meter or so for example used for machine tool assembly).

Yea, just as what I have mentioned it to lyn, the sensors are better off to be those ready-to-use industrial devices for now, with analog voltage/current output ranging from 0VDC to 10VDC (not necessarily, the software people can take care of the calculation for whatever ranges) or 4 mA to 20 mA. We would probably stick to that to ensure quality performance, unless the price goes ridiculously high.

There are some rugged models specifically designed for mobile applications but they aren't the cheapest. Though many are for vehicule levelling and don't have a wide angular range.

You can find anything from low-cost to MIL specs. If you don't know manufacturers you can use Google to get an idea. If your budget is tight you can get a device for OEM integration but you'll waste time and money to develop a case, personnally I'd just get some good COTS ready-to-use device.

Temperature sensors are not a problem, go for something like a Pt100 unless a thermocouple is absolutely required (i.e. where Pt100 is not an option) but TC require some knowledge.

With the price of new, heavy "farm" equipment easily in the $1-500,000.00 USD range the cost of an instrument can be balanced by its value(added) to the operation.

My guess is that this would be important when traversing across a slope.

Another consideration is that the output of the instrument is transmitted back to a central PC/logging device.

We need to "harvest" some more information from the OP.

Maybe something like this......

http://ag.topconpositioning.com/ag-products/x20-application-kits/x20-guidance-and-mapping

additional....

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3231444/

http://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=inclinometer&_sacat=0

Thanks! It is nothing like a steering assist console-not that high end :)

And we are not allowed to purchase anything from ebay or something similar.

We are actually going to find a lot of sensors: some with analog output and some with digital. Eventually they are all going to be hooked up to one microcontroller as all of the output will be programmed and transmitted to a tablet through wifi. In addition, someone else is going to be in charge of designing/making the microcontroller board.

With inclinometers, check if a single or dual axis type is required and if the analog output signal is a trigonometric function of the angle or an already linearized signal. There are also fieldbus devices. There are lots of industrial devices used for platform leveling and similar purposes.

You are absolutely right. The inclinometer only needs to be single axis with voltage/current output signals with ranges.

Use TVS. Available in both uni and bi directional. Cheap. read data sheet for correct part/requirements. Eg...

http://www.digikey.com.au/product-detail/en/1.5SMC62CA-E3%2F57T/1.5SMC62CA-E3%2F57TGIDKR-ND/3847489

Other than the last post, very little has been spoken about the way the personnel must be trained and clothed, but lots of good detailed information about the sensors.

Assuming that the devices are still sensitive, (even ones with built in protection must still be handled carefully) attention needs to be paid to proper bags/boxes for storage and transport.

Handling is also very important and the place where most damage occurs

Also, as already mentioned, the workplace and the tools, must all be correctly bought, organised and used to preclude high voltages developing. Its a science on its own and has its own blog on CR4.

The 1 Meg Ohm wrist strap is a good start, but reduces your area of working/freedom and is easily forgotten after a visit to the toilet for example.

We also had foot straps that contact your skin, usually tucked into your socks at one end, the other end going to contact the floor, usually at the heel. Two of these are best.

But you need special test equipment to actually check that good contact is made, each and every time you put them on. Its surprising how often that the contact was not good enough. Train people to check themselves before entering the work area assuming you buy the tester!!!!

The floor needs to be of a correct type, to bleed any voltage off to ground from your shoes/strap. It can be as simple as connected metal sheets, or there are quality plastic floor coverings that are conductive as well....

Clothing is important, natural fibers are usually best, and you really need to not have anything "man-made" on at all, including socks, plastic shoes (full leather or none!) and underpants, often forgotten. Cotton is good for shirts and trousers or good quality overalls, naturally all free of man made fibers....

To possibly save a small amount of money, the units could have the safety diodes built into the equipment, instead of in the sensor, but I personally find this to be dangerous, but I am not an expert in this area.....what would it save, pennies?

Not doing the job correctly will of course damage sensors.

The biggest problem is not actually a blown sensor, that should be easy to find and replace, but ones that are "only" damaged, that pass all normal tests, but give occasional errors. These can be a real problem to identify and replace.....the time costing far more than the sensor is worth!!!

Remember, if you can see a tiny spark when touching something, that is easily 6000 volts or more!! Some devices are damaged with anything more than 20 volts!!

You may find some of these links and pictures interesting:-

Electrostatic Damage to Components

Ground-Yourself-to-Avoid-Destroying-a-Computer-with-Electrostatic-Discharge

I hope that this assists a little.

Really, Andy!

Read the OP.

The device is a COTS sensor. Already manufactured!

This device is going on a piece of farm equipment, and you want the farmer to wear special clothes and a wrist strap?????????????????

You have completely missed the point, again.

Waiting for your, lame, over the top excuse of why you are right and I am wrong.

I am of the opinion, for many years now, that you give the whole story and leave nothing out.

This allows an intelligent person, once he has this FULL information, to be able to pick and choose what he needs and to discard what he doesn't.

You are of a different opinion, thats all....which is no skin off my nose!!!

Maybe you got a "buffer overflow"? Not enough memory?

Have a great day anyway.......in spite of your overt and aggressive manner!!

Yep. We all have opinions.

It's up to the OP to separate the wheat from the chaff.

100% true, which is why a "full disclosure" is still the best way to go.

By the way, the OP thanked me very nicely for the comment that you were unhappy with.

Now you tell me whose opinion has more value here?

(and which I also place more value on as well! I'll give you a clue, its a name NOT starting with an "L" or ending with an "N"!!)

Yours or the OP?

Thanks, we are aware of that and we have everything needed for preventing ESD on our work stations. However, it is the device I am more concerned about after it is installed on the farm equipment. It might not occur right away-normally happens when in storage. Just trying to figure out ways to prevent any damage caused by ESD.

I wonder and doubt if RTD and thermocouples will be affected by ESD, either bridge type potentiometer transducers. Makes me wanna think more.

If that involves microchip, perhaps it will but what for? If its analog, it would be robust design and simple does not make it that complicated to need a microchip.

RTD and TC are passive components which don't care much about ESD, it's more about what gets connected to their other end.

BTW There's an increasing number of wireless transmission industrial sensors available but they typcially use the free radio frequency bands (like ISM) so there's no guarantee that it will work in a loaden industrial environment. Outdoor in the nature it's not a problem.

Would it not have troubles on distortion from RFI or EMF? I am not so into wireless communication. Sound's like there's alot of trouble and not yet reliably tested.

It may not be exactly what you are looking for, but the TI sensortag had these sensors and communicates over bluetooth, only ~$25.

http://www.ti.com/ww/en/wireless_connectivity/sensortag/index.shtml?DCMP=sensortag&HQS=sensortag-bn

worst case they have a breakdown of what sensors are in there so it may help you look for individual sensors.

Thanks, but we will have to use wifi since bluebooth only works in a short distance, as the farming machineries need to be operated in a distance over 50 meters.

You may opt to use (MOV) Metal Oxide Varistor or (GDT) Gas Discharge Tube to protect whatever you designed transducer for Temperature and Tilting. I assure you, it will protect your invention not just ESD but also other type surges.

A ground strap around the wrist while working on it.

Yes, and don't buy into those wireless ground straps, either. ;-)

Gee, i thought they came with WiFi?

I politely disagree, I recently got a fantastic Bluetooth wireless antistatic wrist ground strap, much more convenient than those ones with a coiled cord. In the combo was also included a brand new wireless HD 3D crystal ball. :)

The OP isn't probably aware of the fact that he'll spend much more time and money trying to develop something himself rather than getting a ready-to-connect sensor + some sort of radio transmitter from some manufacturer.

I would take a look at mobile equipment such as portable, rough-terrain aerial manlifts and cranes that already use the very devices you describe.

I would also contact the field service departments at least three different portable equipment manufactures and ask which sensors are the most reliable before making any purchase recommendations.