Detailed Description

Fully differential and fully automated inputs 1 and 2 are used for voltage and current measurements. You don't have to worry about the kind (AC or DC) of voltage you are measuring. The Multimeter+ can determine it for you and switch between AC and DC measurements automatically.


The following image shows two different voltages measured with inputs 1 and 2. Input 1 value is DC while input 2 values is AC. There is no interference introduced by either of the inputs.

  • Input 3 : Input for Resistance and Capacitance measurements. Capacitance meter has range from 15nF to approximately 2000 uF. Resistance measurements up to 15 Mega-Ohm.
  • Input 4 : Oscilloscope -3dB frequency 55000 Hz.

There is a separate channel, o-scope, to view input signals up to 55 kHz with approximately 380 ksps on PC user interface. Working on improving the sampling speed up to 500ksps. PIC24FJ256GA110 has 500ksps ADC converter, but because the data has to be manipulated and stored the effective sampling rate drops.

The following image shows a sine wave 19130 Hz with a small DC shift:

The following video shows 2.5V square waveform signal tested with Multimeter+. There is a small overshoot as well as a small amout of noise preset.

  • Output : Variable duty cycle pulse generator.
  • Battery : Rechargeable Li-Ion battery.

The instrument has two low frequency high voltage independent inputs for measuring signals and voltage levels below 1 kHz. On the block diagram above they are labeled as Input 1 and Input 2. The inputs are fully differential with over-voltage protection and filtering. Once the analog signal passed through the signal processing circuit it gets digitized by a 24 bit AFE (MCP3911). The MCP3911 is dual channel Analog Front End (AFE) containing two synchronous sampling Delta-Sigma Analog-to-Digital Converters (ADC), two PGAs, phase delay compensation block, internal voltage reference, modulator output block, and high speed 20 MHz SPI compatible serial interface. Voltage readings can be viewed on a built in LCD display or a PC user interface in real time. Input 2 can be set to measure currents up to 0.5A (Currently working to increase measured current range). When current measurement is selected the relay is switched to connect Rsh1 to the Input 2 terminal. There is a separate channel, o-scope, to view input signals up to 55 kHz with approximately 380 ksps on PC user interface. There is a separate input for resistance and capacitance measurements. The on-board pulse generator output can be used to test electronic circuits. Digital sniffer is a work in progress, it will be used to trace digital signals. Internal serial flash memory allows data recording internally for later data view. Galvanically isolated full speed USB port is used for transfer data at 1.2 Mbit/sec from the Multemeter+ to PC user interface. The isolation reduces effects of measurement distortions introduced by a PC. The Multimeter+ runs on a re-chargeable LiIon battery and has an on-board charging circuit.

Galvanically isolated full speed USB port is used for transfer data at 1.2 Mbit/sec from the Multemeter+ to PC user interface. The isolation reduces effects of measurement distortions introduced by a PC.

The instrument has two low frequency high voltage independent inputs for measuring signals and voltage levels below 1 kHz. On the block diagram above they are labeled as Input 1 and Input 2. The inputs are fully differential with over-voltage protection and filtering. Once the analog signal passed through the signal processing circuit it gets digitized by a 24 bit AFE (MCP3911). The MCP3911 is dual channel Analog Front End (AFE) containing two synchronous sampling Delta-Sigma Analog-to-Digital Converters (ADC), two PGAs, phase delay compensation block, internal voltage reference, modulator output block, and high speed 20 MHz SPI compatible serial interface.

On-board LCD display:

The expansion port that will be used for wireless communications and additional hardware, sensors:

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