Great little multitasker – Sonel MPI-506

Simple is better! When examining low voltage electrical networks in buildings, we would like to have an instrument that will allow us to perform all the necessary measurements. At the same time, we prefer not to overpay for an extended meter with functionalities not used in everyday work. Meeting these needs, Sonel has introduced a new multifunctional device for measuring electrical installations.

The idea is to increase ergonomics and to simplify the user's life as much as possible. The Sonel MPI-506 housing is small and handy. It contains a technologically advanced system that allows you to accurately measure the short-circuit loop impedance (also in circuits protected with RCDs), all RCD parameters, continuity of equipotential bonding and protective connections, insulation resistance, network voltage and frequency, as well as the sequence of phase rotation. The large, backlit display guarantees reliable reading, and the 990 memory records eliminate the need to keep notes during measurements.
The housing is made in the IP67 protection class. It is covered with a special elastomeric material, which makes the meter resistant to damage and can work in very unfavorable conditions.

Using the illuminated rotary switch and buttons on the face of the meter, the measurement function and its detailed settings are selected. These parameters are remembered by the instrument even in the event of a complete battery discharge. The settings are changed using the navigation buttons, in a unified manner for all new SONEL S.A. production meters.

When making measurements in sockets, the WS-03 adapter with a mains plug can be used instead of test leads (terminated with probes or crocodile clips). After connecting it, you do not need to define the type of accessory - the presence of the adapter is detected automatically and the meter calibrates itself. To facilitate measurements in industrial sockets (16-, 32-, 63-amp), you can equip with optional adapters of the Sonel AGT series.
MPI-506 meets the requirements of the PN-EN 61557 standard in all measurement ranges. 
 

Short circuit loop measurement

The device enables the measurement of fault loop impedance in networks with a voltage of 180… 270 V (measurements in the L-PE and L-N circuits) and 180… 460 V (measurements in the L-L circuit) with a frequency of 50 or 60 Hz. The rated voltage can be set in the meter (220/380 V, 230/400 V or 240/415 V) - on this basis, the meter automatically calculates the prospective short-circuit current, distinguishing between phase or phase-to-phase voltage.
Loop impedance measurement is possible in the L-PE and L-N as well as L-L circuits. The measuring current is 7.6 A at 230 V (maximum 13.3 A at 440 V). The display shows the result: the measured short-circuit loop impedance, the voltage at which the measurement was made, as well as additional results - resistance, reactance and prospective short-circuit current, available at the touch of a button. All this goes to the device memory.
A very important function of the device is the measurement of short circuit loop impedance in the L-PE circuit, in installations protected with RCDs (with a rated current of 30 mA or higher) without triggering them. Although the measurement is carried out with a very small current (<15 mA), the resolution of the result is even 0.01 Ω, and the possible error slightly exceeds the error of the measurement made with the current 7.6 / 13.3 A.
    If the mains voltage is stable, the measurement takes only a few seconds. With unstable voltage or disturbances, the measurement time is extended by several seconds (with large voltage fluctuations or disturbances, the measurement may take up to 30 seconds) - but only to guarantee an acceptable accuracy of the result.

Residual current device test

MPI-506 enables measurements of RCD parameters of AC and A types. The test can be carried out for circuit breakers with rated currents of 10, 15, 30, 100, 300 and 500 mA; regular, short-delay and selective. In all cases, it is possible to measure the tripping current and time as well as additionally touch voltage and protective conductor resistance. The last two parameters are determined without tripping the RCD.
The triggering current is measured incrementally until the circuit breaker trips. The tripping time can be measured for the multiplicity of the rated current: 0.5, 1, 2 or 5, each measurement with alternating current can be made for a signal starting with the positive or negative half, and with unidirectional current - for pulsating positive or negative current.
You can choose between manual measurements (each measurement triggered separately by the user) and automatic mode (where the user's role is limited to initiating the measurement and switching on the circuit breaker after each tripping). The scope of performed tests is determined by the user. You can select all or a few of the available RCD tests (trip current, trip time for different values of rated current, type of the waveforms); Additionally, during the automatic measurement, it can also measure the short circuit loop impedance (in the L-PE circuit with low current). This allows all required measurements for a given point to be made after one initiation and then saved to a single memory location.
In addition to the manual and automatic modes, the MPI-506 has another, unique function for measuring the time and trip current with one tripping of the RCD. This function measures the tripping current and the tripping time of the circuit breaker for the actual tripping current.

Insulation resistance measurement

Another function of the device is the measurement of insulation resistance. The following measurement voltages are available: 100 V, 250 V and 500 V. A big advantage affecting the user's safety is the automatic discharge of the measured object through the internal resistance, performed after the measurement is completed or interrupted. The measuring range is from 100 kΩ to 599.9 MΩ.

Resistance measurement and measurement of equipotential and protective connections

MPI-506 enables low-voltage measurement of resistance and the measurement of continuity of protective and equipotential bonding in accordance with the requirements of the EN 61557-4 standard.
Continuity control is performed with a current of 200 mA in two directions, with a voltage on open terminals within the range of 4…20 V, up to 400 Ω. The resistance can also be measured with a low current (up to 15 mA) with acoustic signaling in the range not exceeding 1999 Ω. Conductors of any length are suitable for testing. Before the measurement, it is only necessary to compensate them in the meter - after this operation, the device remembers the resistance of the test leads and subtracts it from the measured value, displaying only the resistance of the tested object.
The resistance test functions are protected against possible user errors - an attempt to start the measurement under voltage activates an alarm signal and displays an appropriate warning.

Checking the correctness of PE connection

Using the MPI-506 it is possible to check whether the voltage between the meter's touch electrode and the PE conductor exceeds 50 V. This function is available during the testing of residual current devices and short-circuit loop in the L-PE circuit. To perform the measurement, after connecting the device to the measuring point, touch the START button (the button is made of metal and constitutes a touch electrode). If a voltage above 50 V is detected on the protective conductor, an appropriate warning will appear on the display and a continuous beep will sound. The connection of the touch electrode with the START button causes that the correctness is checked during each measurement of the short-circuit loop impedance (in the L-PE circuit) or RCDs, which is extremely advantageous for safety reasons.

Measurement of mains voltage and frequency

After connecting the instrument to the network, the measured voltage value is displayed before each measurement - except for resistance and continuity. Additionally, after selecting the "U,f" function, the device shows the voltage (range 0.0...500 V) and the network frequency.

Phase sequence indication

Sonel MPI-506 also has a built-in phase sequence tester. For easy connection to three-phase 16, 32 and 63 amps sockets, special AGT series adapters can be purchased. These adapters can also be used for other measurements - short circuit loop, RCDs or insulation resistance.

Memory

The test results can be saved to the memory of the device. Divided into 10 banks of 99 records, it can store up to 10,000 individual measurements. Each record will store the results of several different tests (fault loop, RCD parameters, insulation resistance, continuity) depending on the needs, so that the memory can be used optimally. The user is free to choose the bank number and cell to which he will save the result. After the next measurement, the MPI-506 offers to write to the next available cell, but it also allows to set any other. The memory content is available from the meter display or via a computer - thanks to the built-in Bluetooth module. Using the Sonel Reports PLUS software, you can automatically prepare documentation of the tests performed.

The instrument is powered by four LR6 alkaline batteries or AA rechargeable batteries.

Equipment

The standard equipment of the MPI-506 meter is among others a set of test leads, a lead with a single-phase mains plug, pin probes and crocodile clips. All these accessories along with the meter are in a handy case.
Optional equipment may include, in addition to the described industrial socket adapters, the TWR-1J adapter for measuring RCDs not connected to the installation, the EVSE-01 adapter facilitating the testing of electric vehicle charging stations, 5, 10 or 20 m test leads for checking continuity and a computer software Sonel Reports PLUS for creating test reports.

Author:
Piotr Pawlik
SONEL S.A.