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Probe Start vs Pulse Start HID Bulbs

Compatibility of Lamp Types in High Intensity Discharge Lighting (H.I.D.):
The Difference Between Probe Start and Pulse Start Lamps

When we purchase lamps used for horticultural lighting applications, it is unusual for us to understand exactly how these products operate.  We purchase these items based on habit, recommendation or, sometimes, just on faith that they will work with our current setup.  Unfortunately,  there are differences between lamps, and these differences can cause immediate or long-term problems. Here we will be examining one of those differences: probe start lamps versus pulse start lamps.


In traditional Metal Halide (MH) lamps, probe start ignition is the standard way the lamp ignites.  Inside the lamp there is a starting electrode that has a slight gap.  When electrons pass over the gap they create an arc, and the lamp turns on.  It takes a large amount of energy to ignite this type of lamp, necessitating heavy magnets within the ballast to achieve this energy; much of that energy is lost as heat.  Also, each time electrons traverse the gap small amounts of tungsten are released.  Over time the tungsten residue builds up and the efficiency of the lamp drops.

Pulse start lamps do not suffer from these problems.  There are no starting electrodes to release tungsten each time the lamp is fired up, and there is no need for massive magnets within the ballast to ignite the lamp.  Instead, there are ignitors within electronic ballasts that create high voltage pulses within the lamp.  These pulses shorten the warm-up time for the lamp, they don’t release tungsten and they allow for a lamp with up to a 50% longer life span.  

Because of the differences between the probe start lamps and the pulse start lamps, it is important to use the correct complimentary ballasts.  Probe start lamps should only be used with magnetic ballasts, and pulse start lamps should only be used with electronic ballasts.