PTS Flowbench Forum

I was seeing an unstable reading on the digital manometer and thought it was down to leak and now realise the ametek motors are speeding up and then down by them selves. It is not too much but you can hear them clearly changing RPM which then reflects on the manometer reading.

I am using the following regulator for each motor: It is either THIS or the change of voltage from the WALL?

Could be either.

Depending where you are, the mains voltage can fluctuate by rather a lot as nearby heavy loads switch in and out. Things like electric heaters, and refrigerators and air conditioners can cycle on and off and the mains voltage can go up and down as a result.

A different source of the problem might be your speed control modules. These phase control the mains voltage by rapidly switching on and off at various points on each mains cycle. The switching point may use the mains itself as a phase reference, and any interference (electrical noise) on the mains can cause the triggering point to change unpredictably.

Your controller is probably putting out some big voltage spikes when it switches on and off, and may interfere with other phase controllers. Something may also be be interfering with yours. If you are located in an industrial area, as many engine tuners and flow benches are, the interference problem can be particularly bad and not easy to fix.

The best solution is to NOT use a simple knob controller that uses the mains voltage itself as its phase reference, as most do.

A "proper" more sophisticated phase controller, will have a microprocessor that controls it directly and once set, the phase angle is fixed to what you set it to, no matter how much crap is on the mains.

That will still not fix it if the mains voltage itself is dramatically going up and down.
The next step guaranteed to work would be closed loop control of the actual flow bench test pressure. If you set it to 28 inches (or whatever) that is where it will sit. And it will compensate for any fast or slow variations in incoming mains voltage or gradual changes in motor temperature.

I suggest the first thing to try would be one of Bruce's power controllers with manual control. If its a noisy incoming mains problem, that should give a very great improvement. If its still all over the place, the PTS automatic test pressure controller would be the ultimate solution.

Dear Tony,

The mains voltage from the wall fluctuates between 215V to 235V.

damunk wrote: The mains voltage from the wall fluctuates between 215V to 235V.

In that case, about the only thing that is going to give really good results will be full closed loop test pressure control.

Yeah, with or without voltage speed control the voltage does very around +-4 Volts while the motors are on.

This making the Water H20 pressure fluctuate up and down by 0.05, 0.07

I would assume almost everyone would get this voltage variance from the wall?

My voltage holed mostly steady, but there is a difference in voltage from day to night. My bench makes the best flow volume around 3 in the morning. Every one is asleep and the voltage runs a little higher then.

It depends on your location.
The worst locations for big voltage fluctuations are probably in a factory or industrial area, or way out in the country.

Many engine tuners rent factory space, especially if these is a noisy dyno. And you really do not know what sort of crazy electrical loads your neighbours have.
Some might even run enormous airflow benches they keep switching on and off every few minutes !!

In the suburbs, it can depend on how far away your pole transformer is. Could be right outside, or half a mile away.
Some of us are lucky, others less so.

But if the voltage is going up and down like a yo-yo minute by minute, there is not much you can really do besides spending a bit of cash on automatic test pressure control.
If its set up right, the correction will be very fast and even very large jumps in voltage will be smoothed completely in a very few seconds.

What about a uninterruptable power supply (UPS)? The one I have for my computer runs off smooth battery power but is charged by AC. I know they make industrial strength units but I am ignorant about the size, cost, or specs. In fact, I’m pretty much a half-watt when it comes to electronics.

Anything is possible, you could even buy a large standby diesel generator and run off that.

But the best and the most cost effective solution is still closed loop test pressure control.

Tony wrote:
But if the voltage is going up and down like a yo-yo minute by minute, there is not much you can really do besides spending a bit of cash on automatic test pressure control.
If its set up right, the correction will be very fast and even very large jumps in voltage will be smoothed completely in a very few seconds.

Tony, the voltage is going + 2v and - 2 v which is 4 volt range is and yo-yo ing between 0 and 30 seconds.

I would say doesn't everyone get this small voltage change from the wall using vacuum cleaner motors?

I don't understand how people expect their benches to work like this. Strange.

I wonder what motors 'commercial air flow bench" use?

I have contacted some UPS companies in the UK for some prices.