Herpstat 2 Question

[The Serpent Merchant]

Dimming and pulse are both proportional thermostat modes on Herpstats. The herpstat thermostats have a separate mode for on/off functionality.

The difference between dimming proportional mode and pulse proportional mode is as follows:

Dimming Proportional mode works like an automated lamp dimmer. It varies the amount of power being output to the heat source to regulate temperature.

Pulse Proportional Mode works similarly to an on/off style thermostat but without the swing that is associated with on/off style thermostats. Basically a pulse proportional thermostat fakes what the dimming proportional mode does. It does this by turning the power on and off extremely rapidly (like 60 or more times per second) This is called pulse width modulation. by varying how much time the thermostat outputs power and how much time the thermostat does not it can control the temperature of the heat source very accurately (although the dimming mode is slightly more accurate). This is very different to what an of/off style thermostat does, and shouldn't be thought of as the same thing (because it isn't)

An on/off style thermostat (or a herpstat in on/off mode) outputs 100% power until the thermostat achieves the desired temperature then shuts power completely off until the temperature drops below the swing temperature (usually - 2 degrees from the set point)

So what mode to choose?

dimming proportional is almost always the one to go with. It is the most accurate and is better for the heat source.

Pulse proportional mode should be used when there are grounding problems. Some metal racks hum/buzz when they have heat tape touching them that is being controlled in dimming mode. (Basically you should only use this mode if dimming mode is causing problems)

on/off mode should be used with heat sources that need a constant stream of power, or where accuracy isn't important. (like oil filled heaters)

[BHReptiles]

You people don't know what you are talking about lol.

Dimming and pulse are both proportional thermostat modes on Herpstats. The herpstat thermostats have a separate mode for on/off functionality.

The difference between dimming proportional mode and pulse proportional mode is as follows:

Dimming Proportional mode works like an automated lamp dimmer. It varies the amount of power being output to the heat source to regulate temperature.

Pulse Proportional Mode works similarly to an on/off style thermostat but without the swing that is associated with on/off style thermostats. Basically a pulse proportional thermostat fakes what the dimming proportional mode does. It does this by turning the power on and off extremely rapidly (like 60 or more times per second) This is called pulse width modulation. by varying how much time the thermostat outputs power and how much time the thermostat does not it can control the temperature of the heat source very accurately (although the dimming mode is slightly more accurate). This is very different to what an of/off style thermostat does, and shouldn't be thought of as the same thing (because it isn't)

An on/off style thermostat (or a herpstat in on/off mode) outputs 100% power until the thermostat achieves the desired temperature then shuts power completely off until the temperature drops below the swing temperature (usually - 2 degrees from the set point)

So what mode to choose?

dimming proportional is almost always the one to go with. It is the most accurate and is better for the heat source.

Pulse proportional mode should be used when there are grounding problems. Some metal racks hum/buzz when they have heat tape touching them that is being controlled in dimming mode. (Basically you should only use this mode if dimming mode is causing problems)

on/off mode should be used with heat sources that need a constant stream of power, or where accuracy isn't important. (like oil filled heaters)

I knew roughtly what the differences between the two were (enough to know they were both proportional). I just wasn't sure which was better out of the two. I'll leave it on dimming and when I plug in my incubator, I'll set that one as dimming to. Thanks for your help.

[norwegn113]

Sorry I misunderstood the question. It was late and I thought you were asking about the difference between proportional and non proportional. From now on I just will keep quiet and not answer anymore questions.

[kitedemon]

You would be talking about the proportional and non proportional mode. Proportional mode( dimming ) is a much more accurate way to power your equipment as it fluctuates the power going to the equipment keeping it at a nice steady temp.Usually in the tenths of 1 degree. while non proportional uses an on/off affect.Usually +/-2 or more degrees. The herpstats come with a setting that controls the " swing " of the temperature. I would definitely say that in a situation as delicate as an incubator, I would use the proportional setting without a doubt!

This is absolutely not correct.

Pulse proportional using fast pulses of power to keep stable power. Dimming proportional flutters the amount of power, the volume if you will. They in effect are exactly the same, dimming is a touch more 'smooth' but sometimes hums with a metal rack.

The more technical explanation,
Dimming vs pulse proportional depends on the thermostat. In most cases dimming is going to be smoother. On our pulse proportional mode we actually get a full 0-100% range of pulse lengths and the maximum pulse length is around a second long. Since the max length is short it gives quicker response time and temperature is still smoothly regulated. Energy consumption is basically the same. The only other advantage of pulse proportional mode is that it turns the power on early in ac sine wave while the voltage is low where most dimming styles will turn power on in various times during the ac sine wave. While typically this is not an issue occasionally I hear of someone’s favorite AM radio picking up the pulses and incandescent lights can have a longer life with the pulse mode. It is no different than a light dimmer and a incandescent light in operation. A relay based thermostat like the ranco or Johnson controls will also turn on/off in various parts of the ac sinewave. In fact so does your standard wall switch. I still suggest dimming for everything except for metal racks that exhibit an audible hum in dimming mode.

Dion Brewington
Owner, Spyder Robotics LLC
http://www.spyderrobotics.com