10g 16ms half sine shock test profile

EN 60068-2-27 Shock Testing of Anti-Shock Rubber Mounts

We’ve been vibration and shock testing of some heavy equipment designed for the construction environment. This is one of the toughest environments for product environmental testing. It’s wet, it’s dusty, it gets hot and cold… sometimes all at the same time! Not only that but it’s a very physical environment where rough treatment is the norm.

This customer is well versed in the art of protecting their equipment from such conditions using a robust frame with the key part of the product mounted on beefy rubber shock mounts.

This slow motion footage of captured of the unit undergoing shock testing really shows you just how useful these parts are.

Test was being performed to EN 60068-2-27, 10g shocks with a 16ms half sine profile. There is significant pulse pre- and post-loading as the piezolectronic accelerometer I use has a pretty poor low frequency response and this seems to help.

10g 16ms half sine shock test profile

The use of these anti shock mounts isn’t without issue. In this case, the springiness/stiffness of the anti shock mount combined with the mass of the equipment leads to a resonance at around 25Hz with quite large displacement of the main equipment mass.

The losses in the anti shock mounts causes a damping effect leading to a softer, wider resonance. The equivalent of resistance in an LC resonator causing a reduction in the Q of the circuit.

Compared to a much sharper resonance (caused by a different physical structure) the overall gain is much lower. The tradeoff is selecting a stiffer mount to damp the resonances but at the expense of transmitting more force through to the unit under protection.

25Hz soft resonance vs other sharper resonance

 

 

TWITL – Vibration Testing Automotive ECU

This Week In The Lab: This fuel injector controller has to withstand significant levels of vibration being mounted inside the engine bay of a high performance racing car.

The manufacturer and end user can’t afford a field failure so we are giving it a literal shakedown.

We are also monitoring the live performance during testing of the ECU to check for failure points or changes in the characteristics of the system

Vibration and shock testing applies to a wide range of products e.g.

  • Anything that is mobile or at risk of knocks and shocks in it’s end application
  • Industrial equipment working in a plant room or similar environment
  • Anything with moving parts; how robust is it? Are there unknown resonant modes lurking?

Get in touch to discuss your vibration testing requirements, we’d be happy to help.

 

 

 

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.