TWITL – Shield Prototyping for Sensitive Detectors

This Week In The Lab: prototyping a shielding can for some sensitive detectors.

The customer’s equipment contained some hazardous gas detectors. Despite a good circuit design, one of these sensors wasn’t too happy when tested at industrial 10V/m levels for radiated RF immunity.

EN 50270:2015 imposes some fairly tight limits on the allowed measurement deviation under immunity conditions (depending on the type of gas).

This “fabri-cobbled” shield proved to be a success and a good proof of concept for the customer to take their design forward.

Despite the less than ideal connection made to the PCB ground plane via the screws it was sufficient to achieve a pass.

copper shield for emc emi

 

stainless steel camera system

TWITL – Underwater Camera System Industrial EMC Testing

This Week In The Lab: a nicely engineered underwater camera and lighting system. All beautifully turned, milled and TIG welded stainless steel, this thing can go deep and withstand some rough treatment. It was seriously heavy!

stainless steel camera system

The exact installation environment wasn’t known. Since it was expected to be operated in harsh conditions we opted to test to the generic industrial standards EN 61000-6-2 for immunity and EN 61000-6-4 for emissions.

A Simple EMC Fix

Just one fix required: under 10V/m radiated RF immunity testing one of the positioning motors wasn’t responding to it’s control signals. The control from user to motor was all digital so interference on those lines was unlikely.

The fault finding process was relatively straightforward this time.

We quickly figured out that the problem lay with the optical sensor that detected the shaft position and set the end stops for the range of motion. It was being triggered by the noise which caused it to think that the shaft was simultaneously at both of its end positions.

A ferrite core around the cable and a decoupling/filtering capacitor on the sensor input to the controller stopped the noise from affecting performance.