ExpEYES-17 is interfaced and powered by the USB port of the computer, and it is programmable in Python. It can function as a low frequency oscilloscope, function generator, programmable voltage source, frequency counter and data logger. For connecting external signals, it has connectors on the top panel. as shown in the figure below. The software can monitor and control the voltages at these terminals. Inorder to measure other parameters (like temperature, pressure etc.), we need to convert them in to electrical signals by using appropriate sensor elements. The accuracy of the voltage measurements is decided by the stability of the 3.3V reference used, it is 50ppm per degree celcius. The gain and offset errors are eliminated by initial calibration, using a 16bit ADC. Even though our primary objective is to do experiments, you are advised to read through the brief description of the equipment given below. The device can be also used as a test equipment for electrical and electronics engineering experiments.
IMPORTANT :
The external voltages connected to ExpEYES17 must be within the allowed limits. Inputs A1 and A2 must be within ±16 volts range and Inputs IN1 and IN2 must be in 0 to 3.3V range. Exceeding these limits may result in damage to the equipment. To measure higher voltages, scale them down using resistive potential divider networks.
The functions of the external connections briefly explained below. All the black coulored terminals are at ground potential, all other voltages are measured with respect to it.
The constant current source can be switched ON and OFF under software control. The nominal value is 1.1 mA but may vary from unit to unit, due to component tolerances. To measure the exact value, connect an ammeter from CCS to GND. Another method is to connect a known resistance (~1k) and measure the voltage drop across it. The load resistor should be less than 3k for this current source.
Can be set, from software, to any value in the -5V to +5V range. The resolution is 12 bits, implies a minimum voltage step of around 2.5 millivolts.
Can be set, from software, to any value in the -3.3V to +3.3V range. The resolution is 12 bits.
Output swings from 0 to 5 volts and frequency can be varied 4Hz to 100kHz. All intermediate values of frequency are not possible. The duty cycle of the output is programmable. Setting frequency to 0Hz will make the output HIGH and setting it to − 1 will make it LOW, in both cases the wave generation is disabled. SQR1 output has a 100Ω series resistor inside so that it can drive LEDs directly.
Output swings from 0 to 5 volts and frequency can be varied 4Hz to 100kHz. All intermediate values of frequency are not possible. The duty cycle of the output is programmable. SQR2 is not available when WG is active.
The voltage at OD1 can be set to 0 or 5 volts, using software.
Frequency can be varied from 5Hz to 5kHz. The peak value of the amplitude can be set to 3 volts, 1.0 volt or 80 mV. Shape of the output waveform is programmable. Using the GUI sine or triangular can be selected. WG bar is inverted WG.
Capacitance connected between IN1 and Ground can be measured. It works better for lower capacitance values, upto 10 nanoFarads, results may not be very accurate beyond that.
Capable of measuring frequencies upto several MHz.
This is mainly meant for sensors like Light Dependent Resistor, Thermistor, Photo-transistor etc. SEN is internally connected to 3.3 volts through a 5.1kΩ resistor.
Can measure voltage within the ±16 volts range. The input voltage range can be selected from .5V to 16V fullscale. Voltage at these terminals can be displayed as a function of time, giving the functionality of a low frequency oscilloscope. The maximum sampling rate is 1 Msps /channel. Both have an input impedance of 1MΩ .
Can measure voltage within the ±3.3 volts range. The input can be amplified by connecting a resistor from Rg to Ground, gain = 1 + (Rg)/(10000). This enables displaying very small amplitude signals. The input impedance of A3 is 10MΩ.
A condenser microphone can be connected to this terminal and the output can be captured.
The four connections (+5V, Ground, SCL and SDA) of the 8 terminal berg strip supports I2C sensors. The software is capable of recognizing a large number of commercially available I2C sensors.
The VR+ and VR- are regulated power outputs. They can supply very little current, but good enough to power an Op-Amp.
To get started, a set of accessories are provided with expEYES.