Electrical Spark Meter / Relay

It is an relative measure instrument used to monitor the electrical spark level in electric rotative machines with coal brushes, such as continuous current motors, universal motors, rings motors or slide takings of electrical supply.


- To protect electric machines against damages for electrical spark excess.
- Detection of split brushes or broken in the door-brushes.
- To compare the quality of the brushes for a certain application .
- To determine the correct pressure of the brushes springs .
- To select the best brush type for certain application
     (consequently the maker)
- To reduce stocks of brushes through standardization.
- To adjust the Neutral Line (smaller electrical spark point) of continuous current    motors.
- Establishment of the brushes (film), after collector maintenance.
The instrument besides monitoring the intensity of electrical spark of the electric commutation, it can be adjusted to alarm when a pre-certain level is reached, protecting the machines against eventual damages.

Use instructions

1 - Installation:

The Electrical Spark Meter / Relay, called of here forward as ESM, doesn't need to be close to the motor or electrical spark source.

As it makes relative measure, it can be far, of preference in covered area and without incidence of direct solar light, until a temperature of 45 degrees and without sparkling of water.

The isolator of the connection cables must be compatible with the differences of existent electric potentials.

The coming signal of the electrical spark of the commutation collector / brushes, spreads for the current circuit of the machine, reaching hundreds of meters for the electrical thread, since it doesn't go by transformers, coils, capacitors, thyristors, diodes, etc, that attenuate the signal.

Therefore, with the increase of the distance, increase the attenuation, imposed by the electrical thread.

Chosen the physical point of the installation of ESM, and after the equipment properly adjusted, this will be indicating the electrical spark variation in the motor.

2 - Operation:

ESM is an instrument that was projected for the mensuration of the relative intensity of the electrical spark of motors of brushes AC/DC, or other electrical spark sources just as collectors of electrical energy of crane bridges.

Through the analysis of the frequency spectrum emitted by the physical phenomenon of the electrical spark and the use of its area of larger energy, an electronic circuit works for the visual presentation of the electrical spark intensity in form of bar-graph with LED's.

The scale bar-graph, therefore it indicates the level of intensity of the electrical spark of the motor that is under analysis.

The digital key SENSIBILITY must be adjusted (in the front) for the position 5 and the trim-pot GAIN (in the lateral), so that the half of the scale bar-graph it is illuminated for a situation of electrical spark considered "NORMAL " for the experience and existence in maintenance of electric machines.

THIS IS AN IMPORTANT POINT: the situation of "NORMAL" electrical spark , it is established through visual inspection (to look at the spark of the brushes) in the machines for professionals of experience and existence with commuted electric machines.

Starting from this point, the scale will indicate the RELATIVE LEVELS for MORE ( Increase of the electrical spark) or for LESS (decrease of the electrical spark).

A second electronic circuit with adjustable digital set-point ALARM (in the front), switch off an internal relay.

The alarm level must be adjusted for one or two positions above the maximum level of electrical spark reached in the bar-graph considered in NORMAL situation.

When the electrical spark level increases and it reaches the LED of same number in the bar-graph that is adjusted in the key ALARM, it works a time circuit that will switch off an internal relay, after having elapsed the time adjusted in the trim-pot RETARD (in the lateral).

This RETARD can be varied of 2 to 20 seconds, seeking to avoid that fast electrical outbreaks or electromagnetic interference don't cause incorrect switch off.

The internal relay is maintained energized, therefore in the lack of electric energy or if the electrical spark level drops below the adjusted value in the key ALARM this it is immediately switch off.

3 - Terminals numbering:

1,2,4,6,8,10,11,13 - Not connected

3,5,7 - Signal Input

To connect directly in parallel with two-phase AC/DC or three-phase motor and in any order and without need of electrical insulation (even 1 kV)

9,12 - Power supply of ESM.

    110 or 220 Vac according to specification of the Customer.

14 - Contact relay NC. (Normally Closed)

15 - Contact relay NO. (Normally Open)

16 - Contact relay COMMON.

As described previously, being the ESM electrically supplied (fed) and the electrical spark level considered in " NORMAL " situation, the internal relay is switch on with the contacts 15 and 16 closed.

When the situation of ALARM acts or to lack electric energy, the contacts 15 and 16 open.

4 - Settings:

As the electrical spark is an adimensional physical phenomenon, ( it doesn't have units of measure), ESM shows the level variation (intensity) of electrical spark about of the which was adjusted.

The variables involved in the electrical spark are many such as: pressure of the springs of the brushes, quality of the brushes, momentary overload, split brush, disjoint of the Neutral Line, electric noises of the commutation on power electronics, dirt in the collector, keys of the worn away collector, etc.

Therefore, ESM doesn't show that is an "excessive" electrical spark for a certain condition, but starting from the adjusted point for the experience as " normal " it accuses any variation for more or for less.

Lateral adjusts:

GANHO: GAIN: In cases in that the electrical spark level is low (micro-motors or great distances among ESM and the motor), the trim-pot is adjusted so that it is obtained a significant reading in the bar-graph.

Turn clockwise: it increases the amplification of the signal.

Turn counter clockwise: to decrease.

RETARD: Adjust of the time retard of the switch off the internal relay in alarm condition, varying of 2 to 20 seconds.

Turn clockwise: it increases time.

Turn counter clockwise: decrease time. intense.

Frontal adjusts:

SENSIBILITY: Digital key for the attenuation of the electrical spark signal in cases where the sign is a lot ALARM: Digital key for the choice of the alarm point (coinciding with the scale bar-graph in the level in that wants that the ESM switch off its internal relay).

5 - Operation:

As Electrical Spark Meter: After the electrical power supply (fed) of the ESM, must ignite green LED in the base of the bar-graph.

Switch on the motor (source of the electrical spark), observing the red scale of LED's.

A To adjust the digital key SENSIBILITY and the trim-pot GAIN such a way that the electrical spark intensity oscillations stay among the beginning and the middle of the scale bar-graph.

To adjust the digital key ALARM to the wanted point and the RETARD trim-pot to the necessary time.

As Electrical Spark Meter: ESM accomplishes RELATIVE measures, allowing therefore to verify the conditions of the commutation of the motor BEFORE and AFTER the alteration of its parameters as for example for occasion of a maintenance.

Making the adjusts described previously, ESM is in conditions of accomplishing COMPARATIVE measures.

In case a noisy electric net feeds ESM, (for example where have electrical arc weld machines ) an isolation transformer must be used. (To feed him through a little transformer 1:1)

6 - Technical Characteristics:

- Totally electronic with integrated circuits.
- Scale 0 to 9 with red LED's in bar-graph form.
- Digital frontal keys of SENSIBILITY and ALARM.
- Adjusts of gain for compensation of low levels.
- Adjustment of time of retard for the switch off of the relay.
- Isolation of 1.000 Vac or Vdc
- Direct connection in parallel with the motor and at any distances.
- Feeding 110 or 220 Vac.
- Alarms in the lack of electric energy .
- To attach at panel with screws or DIN thrash.
- Output of the relay in reversible contact of 6 Amperes.
- Dimensions 75x50x100 mm.
- Operation Temperature: 5 to 45 degrees.
- Maximum consumption: 3 watts.

Consult us on Customers that use this instrument