How to Shortlist a Proximity Sensor Manufacturer in India

If you are sourcing proximity switches in India you will get quotations within a fairly narrow price band, and choosing on price alone is how plants end up with a drawer of failed sensors and no recourse.

Here is what we would ask, including the questions that are awkward for us to answer.

1. Do they manufacture, or do they import and relabel?

This is the first question and many suppliers are vague about it. Both models are legitimate, but they give you different things.

A manufacturer can change a specification, build a non standard cable length, adjust a sensing distance and tell you why a part failed. A relabeller can usually do none of these, and when the overseas source changes its design your supposedly identical replacement part behaves differently.

Ask directly: where is this made, and can I visit? A manufacturer will say yes.

2. Which standard, and can they show the test?

For proximity switches the standard is IEC 60947-5-2. Everyone claims it. Fewer can show you the test results for the batch you are buying.

Ask for the test report covering sensing distance, switching frequency, short circuit protection and ingress. If the answer is a generic certificate with no batch reference, you are being shown a marketing document rather than evidence.

If you are exporting the machine, you have a second set of requirements. See sensors in exported machinery and CE documentation, and for hazardous areas, UL, CSA and Zone 0 NAMUR.

3. What is the real lead time, and what is held in stock?

Distinguish three things: what is on the shelf today, what is built to order, and what is imported to order. The quoted lead time usually describes the best case of the first category.

Ask which of the parts on your list are stock items. For a plant spares holding this matters more than price, because the cost of an unplanned stop dwarfs the cost of the sensor. Our spares list guide covers how to decide what to hold yourself.

4. Can they cross reference what you already have?

Most plants are not starting fresh. They have installed sensors from several manufacturers and want to consolidate.

A supplier worth using will take your existing part numbers and tell you which of theirs matches, which is close but different in a way you need to know about, and which they cannot match. That last category is the honest answer and you should expect to hear it occasionally.

We publish our approach in cross referencing imported switches and replacing Omron, Autonics and Pepperl Fuchs parts.

5. Will they customise, and from what quantity?

Non standard cable lengths, specific connector orientations, particular sensing distances, custom housings, private labelling for an OEM. Ask what the minimum quantity is for each.

A manufacturer that will do a non standard cable length in tens rather than thousands is genuinely useful to a machine builder. See custom and OEM manufacturing.

6. What happens when a batch fails?

The question nobody asks at the quotation stage and everybody asks later.

Ask what the warranty actually covers, who pays for the replacement freight, and whether they will analyse a returned failed part and tell you what happened. That last one is the real differentiator, because a supplier who tells you the failure was caused by your installation is giving you information you can act on, and one who silently replaces it is not.

7. Is there engineering support before the order?

Will someone look at your application and tell you the part you have asked for is wrong? Our experience is that a meaningful share of enquiries specify a sensor that will not work, usually because of target material correction or flush mounting an unshielded part.

A supplier who sells you what you asked for is easier to deal with in the short term. A supplier who asks what the target is made of saves you a failure.

8. Documentation

Dimensional drawings in a usable format, wiring diagrams, declarations of conformity, and for export, country of origin and the HSN classification. If these have to be chased each time, factor that into the cost.

Our position

We build proximity switches in Mumbai and have done since 1985, to IEC 60947-5-2. We are not the cheapest quotation you will receive and we will tell you when a part we do not make is the better answer for your application.

If you want to test the questions above on us, send an enquiry and judge the response. That is a more useful comparison than a page of our own claims. There is also a printable supplier checklist and our notes on Indian against Chinese sourcing.