Home > R/C Products > Flight Power Meters > Frequently Asked Questions

Flight Power Meters FAQ

Q. Why should I range check after fitting the FPM?

A. Whilst it is very unlikely the FPM will introduce any new problems it is always wise to ensure the integrity of the R/C model control.

Q. How do I carry out a range check?

A. A range check is best carried out with an assistant to hold the model. Beware the motor may start unexpectedly and the propeller then be a hazard. Always check with the motor off, at half power and at full power. Switch on both R/C transmitter and the model. With the transmitter aerial retracted test the controls. Increase the distance from the model until the controls no longer operate smoothly. This distance should be approx 25 metres. If in any doubt of the R/C link do not fly until any questions have been verified.

Q. What battery packs and motors can I use the FPM with?

A. The FPM can be used with any motor or battery pack combination, LiPo, Nimh, NiCd, brushed or brushless motors etc as long as the maximum voltage and current does not exceed the specifications for the FPM.

Q. I have a multi engined model. Can I use the FPM with it?

A. Yes. If the motors are running from one battery pack position the FPM between the battery and the ESC(s). The FPM will show the total current and power supplied by the battery. With two or more battery packs the FPM must be installed after one pack at a time. It will then show the power supplied by the pack it is installed with. After determining the data needed move it to the next pack. Generally if identical packs, ESCs, props and motors are used the data pertaining to one pack will apply to the other.

Q. What would happen to the FPM if the motor stalls and the current goes above 50 amps?

A. The FPM is designed to measure up to 50 amps however it is unlikely to be damaged by current even considerably above this provided the duration is not too long. The other equipment, battery pack, ESC, motor, is more likely to be damaged than the FPM.

Q. I have accidentally connected the FPM with the wrong polarity to the battery pack. Is this likely to have damaged it?

A. No. Although it is not at all advisable to connect the FPM incorrectly we have found that damage is unlikely due to this. Note that the unit will not work at all if connected with the wrong polarity.

Q. I am receiving data from the FPM unit in the model but no current or power is displayed when the motor is running. Why is this?

A. Ensure the FPM is connected correctly. Battery connections to the battery and ESC connections to the ESC. If this has been transposed the current will flow the 'wrong way' through the unit and not be measured. No damage will occur due to this.

Q. Where should I position the FPM aerial wire in the model?

A. The aerial should be positioned as far as reasonably practical from other metal components in the model and, ideally, at right angles to other wires or equipment such as batteries, motors, receivers and servos. Clearly it cannot be very far from these however practical experience has shown that this is not normally much of a problem.

Q. Does the aerial wire need to be outside the model like the R/C aerial wire?

A. The FPM aerial wire is very short so simply position as far from other metal containing objects such as wires, motors, speed controllers, receivers as practical. Foam, fiberglass and wood will not noticeably effect the range of the FPM

Q. You say the range of the FPM is up to 300 mtrs. Is this enough?

A. Yes, This is based on the radio module manufacturers data however with an air to ground line of sight path a much greater range is normally seen. Assuming there are no problems due to, say, the aerial being masked by batteries or wiring and the hand unit is clear of cars or other metal objects the range is much greater than one would ever fly a model in normal use.

Q. How do I switch off the FPM in the model if it is not being used?

A. The current drawn by the FPM is only a few milliamps and would have no noticeable effect on a battery pack. Since unlike an ESC with a BEC circuit there is no additional source of current drain (the models R/C system) a switch was felt unnecessary. With a 2400 mAh pack it would take 200 hours for the FPM to discharge it.

Q. After switching on the R/C, the model and the FPM I notice there is current drawn and power used even though the motor is switched off. Why is this?

A. The FPM measures the power being supplied by the battery pack. Some power is used by the R/C system, particularly servos, and this shows on the FPM. Note that a servo can draw a peak of as much as one amp hence three servos can draw three amps. With a battery pack voltage of, for example, 10 volts this represents 30 watts just by the servos. Normally this would be the peak power drawn by the servos, not the normal power unless there is a fault with the R/C installation and a servo is being stalled.

Q. Why must the FPM be installed between the battery and the ESC and not between the ESC and the motor?

A. The FPM cannot be installed between the ESC and the motor because when the motor is off there would be no power for the FPM. Similarly at part throttle the FPM would smooth the 'chopped' supply to the motor and show a voltage much lower than is actually being supplied giving an erranous voltage and power reading.

Q. When using the FPM I sometimes get 'No Data being received' message when the model is relatively close. Why is this?

A. The most probable cause is either the FPM aerial on the model being shielded by other wiring or metal objects. Try repositioning this aerial. The aerial on the FPM hand unit similarly can be affected by radio reflections and shielding from metal objects within a few metres including cars, folding chairs, R/C transmitter aerials etc. Try moving the unit a short distance away from these things

Return To R/C Products Homepage

Contact Us

About Us

Sitemap

Links

About Us R/C