Caddsdown comes to Schaffner for conducted immunity testers

"The criterion used in selecting our test equipment was quite simply to buy the best; and when it came to powerline and conducted immunity testing, that meant Schaffner."

The impetus for Caddsdown came from Business Link SW, which brought together 20 small- to medium-sized businesses on a "mutual support basis" with the University of Exeter. Financial support was provided by Torridge District Council and a grant from the EU. The centre is non-profit-making: each of the 21 shareholding organisations receives a monthly time allocation, which can be used for R&D or general precompliance testing - or, in the case of the University, as the practical element to its EMC courses. Non-shareholders can hire the centre (fully staffed) at £450 per day.

The centre prides itself on providing comprehensive EMC testing facilities to a range of standards, including radiated and conducted emissions and immunity testing in its anechoic chamber, with further radiated testing at its open area test site which is calibrated at both 3 and 10m. Bench testing includes bursts, transients, ESD, harmonics and flicker, and this is where Schaffner came in.

Says Wilson: "Our choice of equipment was driven as much by a confidence building exercise as anything else. Originally, this meant we wanted our users to be reassured that the results they were getting came from equipment from industry leaders. The thing that has surprised us is the overwhelming level of technical support we have received from our suppliers".

Schaffner equipment in use at Caddsdown covers a full range of conducted immunity standards:-

• electrostatic discharges to IEC1000-4-2 using the NSG435 ESD generator;
  
• surge pulses to IEC1000-4-5 using the NSG2050;
  
• and bursts to IEC1000-4-4 using the NSG2025;
  
• harmonics and flicker to IEC1000-3-2 and -3, using the latest ProfLine 3000 automatic test system.

• The NSG435 is the market-leading handheld ESD tester. All functions are microprocessor controlled, accessed from a rear-mounted liquid crystal display with five softkeys. In standard form, the instrument comes equipped with a 150pF/330W discharge network. Voltage can be adjusted in 100V steps using the softkeys. Dynamic accuracy is better than ±5%.

• The NSG2025 burst pulse generator is available with burst amplitude ranges from 200V to 4.4 or 8kV, frequency ranges of 100Hz to 500kHz or 1MHz, and network current of 16 or 30A. Users can set a number of parameters, such as variable burst repetition time, a variable number of spikes per packet and the ability to sweep through the frequency band, giving the ability to identify critical frequencies.

• The NSG2050 surge generator is available with a range of plug-in pulse modules suitable for testing to all common European, US and IEC industrial, domestic and telecomms standards. Manual control of the instrument via the front panel offers access to the entire range of instrument functions. The LCD gives continuous display of instrument status and menu options. Standard pulses can be selected according to the modules installed, or custom pulses created by modifying the standard ones. Tests can be saved for future use.

The ProfLine system at Caddsdown now runs the latest version of PowerStar EMC, developed from Schaffner's market-leading PowerStar power supply ATE software. However, before this was installed, a great deal of support was needed. "We must have spent hours on the phone with Schaffner both in the UK and Ireland", admits Wilson, "but every question was answered, even if it meant talking to the programmers!".

In its first 18 months of operations, bookings for the centre have steadily increased, with shareholders taking their full allocation of time, and outside companies taking an ever-increasing share, providing useful revenue. Many of these have come from outside the expected catchment area, indeed as far afield as Sussex and even France.

In fact, Schaffner itself made use of the facilities at Caddsdown earlier this year for emissions testing on the footprint filter custom designed for the new Toshiba VFS7 family of variable frequency AC inverters.

For the future, Caddsdown plans to move towards NAMAS accreditation and Competent Body status.