| Author | Message | ||
     Fasted |
 i want to completely load my system with headlights, turn signal, brakelight, and heated clothing to measure total amperage used. how do i hook up a multimeter to accomplish my simple task? | ||
| Sparky |
The most accurate way would be to put a current shunt which is a calibrated resistor in series with the main fuse/circuit breaker and read the voltage drop across the shunt. Otherwise, a clamp-on current probe should be accurate enough. | ||
| Iamike |
Your manual will give the generator output, then go through the list of loads and you will come pretty close. It lists the draw of the engine requirements and each bulb. On my S3 I added a pair of 35w fog lights that darn near maxed it out. I rewired my front turn signals (10w ea) to be on all the time and then blink off with the signal. I realized that I was maxing the system out after I installed a voltmeter and it would drop down to 12.5-13v when I had the fog lights on. I've never run my battery down but I did lose a stator once. I have thought about switching the front signals to LEDs which would reduce the load. The next step would be swapping out the taillights since mine has 2. | ||
| Reepicheep |
Generally, you have to break the wire to measure amperage. To measure voltage, you don't have to really "do" anything. You can add a device in parallel that flows virtually *no* current, but gets all the voltage, and you can measure the voltage. Kind of like running a straw out the bottom of a dam to measure water pressure... you can measure it with little things without killing anyone. To measure current though, you have to flow the current through the meter. So if you want to measure 50 amps, you need a wire and meter capable of carrying 50 amps. Thats a big wire, at least for what you are used to with a multi meter. There are other ways to measure current... I just got a "clamp on" meter from harbor freight, which was an entertaining diversion at $8, but that does not really work very well (and would not work for this application anyway as it is DC). These clamp on meters measure an inductively induced voltage by putting a coil around an (unbroken) wire carrying current. You also have the problem that current generation varies with RPM. So you will need to wind the engine out before getting a measurement... You are going to have a hard time finding a high enough power resistor to hook up as an inline load (that you could then measure voltage drop across). One "guess" approach might be to find out the characteristic impedance of the stator wiring (which will be something like .01 ohms per foot), and try and measure the drop across that (volts = amps times impedance). That way you are not introducing any new bits into the system. Just tapping off a few known points. A good digital volt meter will probably have the necessary accuracy for the voltage drop, but you will have a hard time getting an accurate enough characteristic impedance. Another way might be to put an oscilloscope on the stator output.... something I always wanted to do. You might be able to see some ripple from the shunt regulator, and compare that to where in the duty cycle it "triggers the shunt", and use that to calculate how much margin you are using. Come to think of it, if you do want to break the circuit and measure current, you might be able to do it between the voltage regulator and ground. That way, you are only measuring "wasted current" and not all generated current. That might bring it down to the levels that won't bake your multimeter... I think my Fluke 77 will handle 15 amps (and I have shot as much as 70 amps through it for one brief shining moment and it survived). That approach would also let you slowly build up... start at idle, where the bike needs just about all the current it can produce, and measure, and increase RPM's until the meter starts to smoke  . Then either add more load, or add a bigger meter . That would be kind of a neat experiment. An "amps being shunted" gauge. You would have to be careful though, if you end up generating any voltage between the VR and ground (say by adding an inline light bulb, which is a poor mans 100 watt resistor) you will be "raising" regulated voltage on the bike... which could bake things. |
