Bad weld with magnifier relay switch

Reed Relays generally have a higher Carry Current rating than their ‘hot’ Switching Current rating. It is usually during ‘hot’ switching where contact damage occurs due to the resulting arc across the contacts as they open or close.

A severe current overload will quickly melt the contact area causing the two surfaces to fuse together creating a hard weld as soon as the contact closes. Less severe current inrushes will cause a milder weld or gradually build up a ‘pip’ on one contact and erode a ‘crater’ on the other according to the direction of current flow. These can eventually lock together. Arcs can occur when contacts open, particularly when the load is inductive and Back EMFs from inductive loads should always be limited, usually by a simple diode in the case of DC loads or by a Snubber or Varistor in the case of AC loads.

One way to reduce or remove these issues is to ‘Cold’ switch. This is a common technique in Test Instrumentation, where the current or voltage stimulus is not applied to the switch until after the relay has been operated and contact bounce finished. In the same way, the stimulus is removed before the contact is opened. In this way, there will be no arcing or switched current inrushes and the relay will achieve maximum life, often into billions of operations.

When calculating the delay time between switching on the relay coil and applying the current to the switch, it is important to consider the effects of high ambient temperature if this is likely to be encountered. The maximum operate time and bounce figures given on the data sheets are at a 25°C ambient level. At higher temperatures, the resistance of the coil winding will increase at a rate of 0.4 % per °C, this being the coefficient of resistance of the copper coil wire. There will therefore be a corresponding fall in coil current and the level of the magnetic field that is generated to operate the reed switch. This lower drive level will increase the operate time slightly.

The timing figures on Pickering data sheets are normally quite conservative so this is unlikely to be an issue up to the normal ambient specification of 85°C. However, if there is any additional self-heating within the relay due to a high carry current and the switch resistance (I²R Watts), it will be necessary to consider this and allow a little more time before turning on the current through the switch.

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Pickering Series 115 2 Form A,

Pickering Electronics will be showcasing its latest high density range, including the addition of two pole reed relays to their established Series 115, at Semicon Korea on 8 – 10, February 2017 on stand 2811.

The newly released Series 115, 2 Form A relays can switch up to 15 Watts, 1 Amp and require a board area of only 0.15 x 0.4 inches (4mm x 10mm), an increase of only 50% over the single pole version. These relays are the ideal choice for high density two pole matrices and multiplexers.

Two switch types are available. Both types have sputtered ruthenium contacts for long life and high reliability. Switch type number 1 is better suited for general purpose applications. It has a layer of copper beneath the ruthenium to help dissipate the heat from the contact area. This gives an improved current inrush handling ability. Switch type number 2 should be chosen for low level or ‘cold’ switching applications.

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NEW SERIES 67 and 68


New Series 67 and 68 High Voltage Reed Relays for up to 10kV

• PCB Mounting with option of flying lead switch connections
• Robust tungsten plated vacuum switches
• Plastic package with internal mu-metal magnetic screen
• Ideal for cable and transformer test or other high voltage applications

Pickering Electronics are pleased to announce the introduction of the Series 67 and 68 range of high voltage reed relays. Similar in specification to the long established Series 60/65 and 62/63, these new relays are manufactured in a Single-in-Line (SIL) format using former-less coils which dispense with the more usual coil supporting bobbin allowing a smaller package than similar rated devices. The Series 68 has flying leads for the switch connections which allow the high voltages to be kept away from the printed circuit board (PCB). The Series 67 has PCB connections for all terminals. The unusual package design does present some interesting packing possibilities for high density applications such as multiplexers and matrices in instrumentation and test systems. The relays are suitable for high voltage transformer and cable test and some electro-medical applications such as defibrillators.


New Series 119 Micro-SIL Relays for up to 3kV

• Sputtered Ruthenium vacuum switches
• 1 Form A at 1, 2, or 3kV plus 2 Form A at 1kV
• Plastic package with internal mu-metal magnetic screen
• Ideal for Mixed Signal ATE, Cable Test or other high voltage applications where space is at a premium

Pickering Electronics are pleased to announce the addition of the Series 119 high voltage Micro-SIL relay to our range.

This is the smallest high voltage reed relay currently available and features sputtered ruthenium switches which makes them suitable for low levels as well as high voltage stand-off. The single pole 1kV version is pin and package compatible with the popular Series 109P so it may be possible to increase the functionality of some existing designs.



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