voltage question 110 on shore power 100 on inverter???

wa8yxm wrote:

BFL13 wrote:
If the inverter is MSW your ordinary voltmeter will read 97 or so it varies. You need a fancy meter (RMS something) to get the "real" voltage.

If the inverter is PSW then it should read the full 120, same as shore power.

I will second that. The fancy meter is called a "True RMS Meter" Rms means "Root, Mean, Square. and if you were to look at the curve of the power output on a scope it is the area "under" the curve (Between the line of power and the base or zero line)

All very confusing but many meters are "Peak reading" and due to the Flat Top of the Modified wave... The peak is lower for the same area.

virtually all analog meters as you point out are peak responding, RMS calibrated for a 50-60 Hz pure sine wave. any other signal gives you pretty inacurate results, like trying to measure a MSW inverter output.

While I have a couple of old simpson analog meters, most of the time I dig out my digital meter. more rugged, less likely to be damaged.

With the advent of decent low cost RMS converter circuits with bandwidth at least into the 10's of KHZ making a digital meter than is RMS responding, RMS calibrated is pretty easy to do and gives accurate enough results for most power line measurements RV'rs need to make.

Many also have features like min/max/average with a 1ms or so sampling window that will allow you to capture pretty narrow pulses and a delta function that will let you see change vs baseline.

But there are still cases where I like to look at a signal with an analog meter.

The cooking power of a microwave on MSW is dependent on the peak voltage of the waveform, which varies with different makes/models, and the DC input voltage to the inverter. So users with different makes/models will see different results, and an individual user will see a difference depending on the battery SOC. In some cases this behavior is an advantage, as a user with a smaller battery or inverter that won't support the full cooking power might be able to run the microwave from the battery at the reduced power, then have the full cooking power available when on shore power.

With the old-school simple power supply design found in most microwaves, which uses a half wave rectifier to charge a capacitor, the peak voltage of the waveform determines how much power the magnetron produces.

BFL13 wrote:
If the inverter is MSW your ordinary voltmeter will read 97 or so it varies. You need a fancy meter (RMS something) to get the "real" voltage.

If the inverter is PSW then it should read the full 120, same as shore power.

I will second that. The fancy meter is called a "True RMS Meter" Rms means "Root, Mean, Square. and if you were to look at the curve of the power output on a scope it is the area "under" the curve (Between the line of power and the base or zero line)

All very confusing but many meters are "Peak reading" and due to the Flat Top of the Modified wave... The peak is lower for the same area.

2oldman wrote:

BFL13 wrote:
the Sharp MW that came in our 2003 5er ran ok on MSW and so do other newer ones we have tried at times by Danby and Kenmore. Perhaps there was a change in MW design in the mid-90s or whenever?

It's often reported that they run, but at 1/2 power.

I did some tests on that measuring temp vs time in a cup of water and it did take longer to heat up with MSW. Was better than 1/2 time ISTR.

With actual use compared with at home, things seem to only take a little longer, so you hardly notice any difference. In fact, it takes the same time to get things hot enough to eat we find. With PSW you could get things too hot in the same time. All very subjective and situational.

So if anybody says his MW works fine on MSW it does work fine for him. YMMV, you are the only one who would know that, depending on what you do with MWs.

BFL13 wrote:
the Sharp MW that came in our 2003 5er ran ok on MSW and so do other newer ones we have tried at times by Danby and Kenmore. Perhaps there was a change in MW design in the mid-90s or whenever?

It's often reported that they run, but at 1/2 power.

2oldman wrote:
I'm wondering if your MW actually does 'work fine' with that inverter.

The Dometic RV microwave that came in our new to us 1991 rig will not run on MSW at all. Runs ok on PSW. (MW has brown wood grain cover and no turntable as indication of its age) It has been replaced with one that will.

However the Sharp MW that came in our 2003 5er ran ok on MSW and so do other newer ones we have tried at times by Danby and Kenmore. Perhaps there was a change in MW design in the mid-90s or whenever?

Still looking for that peak-to-peak digital meter. Now THAT would show some whoopee between a true sine wave and pseudo wanna be's. Compare values between it and a -true- RMS reading while using an inductive load, the clouds part, the light shines down and all* is explained.

* "Oooooooooooo Lookie"

I'm wondering if your MW actually does 'work fine' with that inverter.

MEXICOWANDERER wrote:
Hah! Say the words "Parallax correction mirror band" and the duck comes down and gives you fifty dollars.

Spoken like a true game show host George. Groucho would be proud. Marx my words.

Hah! Say the words "Parallax correction mirror band" and the duck comes down and gives you fifty dollars.