Ok lets go by the original post and dissect it.
I am done machining my Edward 5 and started the construction of the display base.
The base includes the fuel and gas tanks, a drawer for all the special keys, extractor a whatnot that goes with the engine and the powering and monitor system for the 5 glow plugs.
Ok 5 glow plugs and monitoring each plug, lots of options here.
I plan to heat the plugs with AC. A 24VA transformer rewound with 5 secondaries for about 1.5V each.
I want to sense each plug because if one goes bad I have no indication other than possibly rough running of failure to start. I have to disconnect them all and use my ohm-meter to find the bad plug.
Normally when someone says they are going to use a 24VA transformer it is assumed they are going to use a transformer that is normally used for things like doorbells, 110/220 in, 24 volts 1 amp out for a rating of 24 watts or 24VA. Since glow plugs are normally rated at 1.5 volts (standard) and the current consumption is tied to the applied volts and the resistance of the platinum wire one just needs to ensure not too overheat the glow wire. He also stated that he is going to use AC not DC voltage to heat the plugs which is ok but, 1.5 volts AC is too low. One must include the PFC (power factor correction) to do this properly. He also wants to monitor each plug to see if it is open or closed or maybe even dieing. I have to assume it is for opens because a standard multimeter is not sensitive enough to show minor deviations in resistance. One must use something like a Kelvin (4-wire) resistance meter. In retrospect since the OP has years of experience making 500 transformers then he would know that the best setup for 1 primary and 5 secondaries would be to wind a toroidal transformer (better cooling and easier to wind) and not to use a doorbell transformer (assumption). Using a switching power supply would be the best but, it is also the most expensive. As for monitoring each plug, now that would/could be anything from cheap to expensive, he needs to elaborate more.
I could use only one secondary but it will be too too thick a wire to bend sharply on the bobbin and would require a 5 floating shunts on the plugs tips side.
With 5 secondaries all the shunt can be grounded and the secondaries are smaller gauges.
But all this is not the reason of this post, just background for the real question.
Ok your opinion but, one still needs to match the secondaries to the current draw of each plug, regardless if one ties the grounds together. Whats wrong with running 1 heavy gauge ground wire to the motor?
First a bit of history
those of us old enough will remember that Glow Plugs use to be 2V, back then the only battery available was Lead-Acid. A single cell charges at around 2.3V, as soon as disconnected from the charger they fall to 2V and stay there until discharged to 1.8V. End of story.
Then came those wonderful NiCd, the high discharge rate made it possible to use a small capacity cell that could be coupled to the plug connector and the plug igniter stick was born.
I suppose, but have no direct knowledge that the old 2V plug would work enough on a freshly charged NiCd cell.
Everybody called the NiCd cell a 1.5V cell and the 1.5 Glow plug was born.
NiCd/NiMh are rated at 1.2 volts, not 1.5, they safely charge at 1.5 volts. I used to use the old dry cell battery that was 1.5 volts. Glow plugs as far as I know since 1974 (when I got into glow engines) they have always been rated at 1.5 volts. I used the old dry cell battery that was 1.5 volts and that's where it came from. I use NiCds even now (personally and commercially), there are tons of them out there and they are still the best rechargeable batteries for cold climates, below freezing, and still safer than Lithium.
A NiCd cell is charged until it reaches 1.5V. When connected to the load it quickly drops to 1.4V
Depending on the discharge rate I/Capacity and temperature it can be discharged down to 1-1.1 V
During a slow discharge the cell voltage is averaging 1.35V on a brisk discharge we may say the average voltage is about 1.2V.
Calling NiCd cell a 1.5V cell is just marketing talk, technically speaking convey zero information.
I don't know of any manufacturer that rates NiCd/NiMh at 1.5 volts, they are always rated at 1.2 volts.
Now to the question: Has any one ACTUALLY measured the voltage and current on a properly working, capable to start the engine, plug powered by a middle of the charge stick or single cell NiCd?
This makes no sense at all, because nobody uses glow plugs from the 60s and plugs are rated for different heat/watts and sometimes voltage. The compression and nitro content usually dictate the plug heat type. Besides this info is easily found on the internet. I suggest contacting the manufacturer of the glow plug you want to use and get their recommendations, same as I did with Fox.
All the other data is just guessing.
You got that right, I'd say most of it.
There are 2 websites that have tons of valuable information available: