With a high resistance in the outside circuit, the deflections of the ammeterwill be small, but such as they are, they will fairly accurately represent the electromotive forces which produce them.
In marking the scale, an ammeter is placed in the circuit of an electrolytic cell and the position of the pointer is marked on the blank card which lies beneath and which is to serve as a scale (Fig.
Take corresponding readings on a standardammeter and mark the figures on the dial.
This is done by connecting it in series with another standard ammeter which has the scale marked in known quantities.
How to Make an Ammeter [203] The outside case of this instrument is made of wood taken from old cigar boxes with the exception of the back.
Three switches, B, C and D, are employed for changing the connection of the ammeter and wattmeter in either one of the two lines.
With the primary circuit open, the ammeterindicates the exciting or no load current.
If there be much difference, however, in the voltage of the three phases, the ammetershould be switched from one circuit to another, and the current measured in each phase.
The ammeter and the current coil of the wattmeter will then be connected to the middle line of the motor.
In making resistance measurements of large transformers by the drop method care should be taken to allow both ammeter and voltmeter indications to settle down to steady values before readings are taken.
Wiring diagram for Crouse-Hinds radial ammeter switch as illustrated in fig.
It is practically the same, except for the introduction of an extra ammeter and a compensator in each of the outside wires, and in the use of a four pole switch in place of the two pole main switch.
This may conveniently be done by noting the deflections at short intervals on an ammeter connected in circuit, and also the readings on the dial of the recording wattmeter during this period.
If the resistance X{i} be known, and the ammeter be suitable for use with alternating current, the switch and R may be dispensed with.
Connect the primary of the transformer to the line as shown, and carry normal secondary load by means of a bank of lamps or other suitable resistance, until full load secondary current is shown by the ammeter in the secondary circuit.
The 150 scale ammeter may be left in circuit for an indefinite length of time at one-third its full capacity, and for three minutes at one-half its full capacity, with a negligible error.
In the battery circuit there should be an ammeter having a scale on both sides of zero, to show whether the battery is being charged or discharged, as well as the value of the current.
An ammeter with suitable scale should be inserted in the battery circuit to indicate the current.
An ammeter and rheostat may be placed in this charging circuit if the current is to be varied, or a fixed connection may be substituted on the base of the rectifier if it is to be used for the maximum duty of 8 or 16 amperes.
The switchboard is provided with a combination volt-ammeter which shows the voltage of the battery, the ampere charging rate of the dynamo and the ampere discharging rate of the battery.
Another similar ammeter is required in the circuit between the dynamo and the battery, to show the direction and amount of current.
A third ammeter is desirable in the lamp circuit, to show the total current supplied to the lamps, but it need only indicate on one side of zero, since the current there always flows in the same direction.
This is done by putting an ammeter in the circuit.
The reason for this is that the voltmeter registers the pressure, the power, or the difference of potential between the two sides of the cell, and the ammeter shows the quantity of current flowing over the wire.
The voltmeter is placed in a short circuit between the two terminal wires, whereas the ammeter is placed in circuit with one of the wires.
A relay snapped, and instantly theammeter jumped to read 4500 amperes.
The heavy coronium spring grew warm and began to glow dully, while the ammeter dropped slightly because of the increased resistance.
An ammeter and a heavy coil of coronium wire were connected in series with the coil, and a kilovoltmeter was connected across the terminals of the relux plate.
Arcot glanced in surprise at the heavy-duty ammeter in a control panel.
Ag is an ammeter used to measure the strength of the total current, and Vg is a voltmeter that indicates the electro-motive force of the current passing out to the cars on the various lines.
The ammeter is connected in series and the voltmeter in shunt.
An ammeter in the circuit shows increased current as the cells are added.
In fact, a voltmeter is an ammeter which has had its shunt removed or disconnected.
It is like an ammeter in construction and appearance.
In other words a voltmeter is connected in shunt, while an ammeter is in series with the circuit as is shown in Fig.
With an ammeter one may study the change produced in the amount of current flowing in a wire when a change is made in the wire conducting the current.
It is called the volt-ammeter method since it employs both a voltmeter and an ammeter.
For example, if one measures with an ammeter the current flowing from a dry cell through a long and then through a short piece of fine copper wire, it will be seen that less current flows when the long piece is used.
Current's all right, I've tried new tubes, and the wave meter and ammeter tests are O.
The filament oscillates and the ammeter registers and yet I'll bet there isn't a wave going out.
The sensitiveness of such a thermal ammeter can be made sufficiently great to detect a current of a few microamperes.
The drop across the ammeter was taken into account in the voltmeter readings.
The ammeter was placed beyond the voltmeter in order to get the true current taken by the lamp.
To regulate the flow of current through the battery move charging lever R to the right slowly until ammeterindicates the correct charging current.
The ammeter after the first rush of current may not show any current as passing, or it may show a reverse current.
Move regulator R to the extreme right step by step and note that the ammeter continues to return to zero, which indicates that the film on rectifier electrodes is formed properly.
When you tune the transmitter so that the ammeter shows the largest amount of current surging in the aerial wire system you can consider that the oscillation circuits are in tune.
Telegraph Transmitter] Now connect the end of the tuning coil that leads to the ammeter with one end of the .
The ammeter is connected in the aerial wire system, either in the aerial side or the ground side--the latter place is usually the most convenient.
This is the same kind of a hot-wire ammeter already described in connection with the experimental set, but it reads to 5 amperes.
An ammeter that measures a current by the one-thousandth of an ampere.
The filament voltmeter is connected across the filament secondary coil terminals, while the plate milli-ammeter is connected to the mid-taps of the plate secondary coil and the filament secondary coil.
To do this you need only to use a voltmeter across the filament terminals instead of an ammeter in series with it; then regulate the voltage of the filament with a rheostat.
Don't operate a transmitting set without a hot-wire ammeter in the aerial.
The microphone can be connected in the ground wire and the ammeter in the aerial wire and the results will be practically the same.
This instrument is also called a hot-wire ammeter because the oscillating currents flowing through a piece of wire heat it according to their current strength and as the wire contracts and expands it moves a needle over a scale.
Eliminating Motor Interference--= Connect the ammeter condenser to the spring clip at the end of the wire containing the fuse holder by means of the self-threading screw on the side of the spring clip.
They should be connected in one circuit and the deflection of the ammeter observed when the armature is held stationary, and when it rotates with various loads.
The voltmeter cost $7, and the ammeter $10; and the switches and fuses could be had for $5.
With all storage battery outfits, an ammeter (or current measure) is supplied with zero at the center.
An ingenious mechanic can construct such a radiator, experimenting with the aid of an ammeter to ascertain the length of wire required for any given stove.
I have connected the ammeter so that it will indicate thousandths of an ampere, and you see that the needle moves only slightly.
Before we replace the face of this ammeter I must call your attention to a wire running by a short cut from one binding post to the other, s (Fig.
Let us then connect one dry cell with the ammeter and place the tip of the tongue between the bare ends of the wire at T (Fig.
The ammeter in the engine room showed that 7 amperes of electricity were sent through the motor of the elevator to bring us up.
We will put in a fresh piece of wire and connect also the ammeter in the circuit (Fig.
The volt meter shows 25 volts of pressure, and the ammeter shows 3 amperes of current.
We put the 112-volt current upon this wire of the iron, and according to the ammeter it passed 4 amperes.
We next substitute for the ammeterat C the primary and secondary coil of the telephone.
I connect it for an instant as an ammeter you see it indicates twenty amperes.
The ammeter shunt was removed so that all the current went through its armature.
Meanwhile I connect two wires to my sensitiveammeter and let their free ends brush along on the rings e and f.
I now throw on the alternating current, and the ammeter shows only a small fraction of an ampere.
I asked one of the boys to tap the tube slightly with a lead pencil so as to jar the metal filings, and as soon as he did so the needle of the ammeter went back to zero.
The ammeter indicated only half as much as before, that is .
It will be necessary to obtain the use of a direct-current ammeter for this purpose.
The method by which this tuning is achieved is to insert in the portion of the aerial below the spark balls, between it and the earth, a hot wire ammeter of some form.
Accordingly, the inductance and capacity of the lateral branch of the transmitter is altered until the hot wire ammeter in the base of the aerial shows the largest possible current.
Cutout does not open until ammeter indicates a discharge of three or more amperes (in addition to the ignition discharge).
Should the ammeter indicate "charge" the battery connections have been reversed, or the ammeter connections are reversed.
The amperes indicated on the ammeter should be the greatest when the main headlamps are burning bright.
After a slight movement of the ammeter pointer indicates that the cutout has closed, speed up the engine gradually.
If no other trouble exists, theammeter will indicate a charging current at speeds above 8-10 miles per hour.
The ammeter (either that on the instrument panel, or a special testammeter connected in series with the battery) will indicate several amperes discharge, this being the current taken by the ignition system.
If the ammeter needle jumps back and forth and the cutout opens and closes rapidly, the polarity of the battery and that of the generator are not the same.
Ammeter should show three to five amperes charge with lamps burning.
If the ammeter shows a charging current of three amperes or more as soon as it closes, the cutout is at fault.
If the voltmeter pointer does not return to the "0" line when the cutout points are separated, or if the points were not found to be stuck together, disconnect from the cutout the wire which goes to the ammeter or battery.
The voltmeter and mil-ammeter were read every few minutes, the water collected in the water-meter, carefully weighed, and the temperature differences as measured on the two mercury thermometers were recorded every 4 minutes.
The mil-ammeter is so adjusted as to give a maximum current of 1.
The "soft-iron" ammeter can be used for both direct and alternating currents, is inexpensive, and is sufficiently accurate for commercial use.
For direct-current measurements where a high degree of accuracy is of first importance, a "moving-coil" ammeter is invariably used.
Almost invariably an ammeter gives its full-scale reading when a small current, say of the order of one-tenth of an ampere, is passing through the instrument itself.
Instruments of the ammeter type can also be used as ohmmeters.
Another kind ofammeter known as a thermo-ammeter works on quite a different principle.
This latter is simply the product of the voltmeter and ammeter readings which gives the watts just the same as in direct current.
The watts obtained by multiplying together the simultaneous voltmeter and ammeter readings.
A virtual current is that indicated by an ammeter regardless of the phase relation between current and pressure.
Combining these curves, the dotted curve in the figure is obtained and which represents the resultant current that would be indicated by an ammeter placed in the primary circuit of the transformer.
An effective current is that indicated by an ammeter when the current is in phase with the pressure.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "ammeter" in a variety of sentences. We hope that you will now be able to make sentences using this word. Other words: accelerator; auto; automobile; equipment; generator; instrument; meter; muffler; parts
