2.1.5. LCR meter¶
This application will turn your Red Pitaya into an affordable LCR meter. It is the perfect tool for educators, students, makers, hobbyists and professionals seeking affordable, highly functional test and measurement equipment. The Resistor, Capacitors and Inductors are basic components of all electrical circuits and working on your projects you will definitely need to measure some components laying around on your working bench. The Red Pitaya LCR meter will enable you to do that quickly and accurately just by switching from one application to another.
To use the LCR meter application an additional extension module is needed. Module can be purchased from Red Pitaya store.
All Red Pitaya applications are web-based and don’t require the installation of any native software. Users can access them via a browser using their smartphone, tablet or a PC running any popular operating system (MAC, Linux, Windows, Android and iOS). The elements on the LCR meter application are arranged logically and offer a familiar user interface similar to bench LCR meters.
The graphical interface is divided into 6 main areas:
- Hold/Run button: It is used to start and stop measuring. Log data button: When selected, the measurements of parameters selected in the “Data options” field are logged in the table shown in area 6.
- Data options panel: It is used for selecting the desired parameter for which the measurement will be displayed on the Main window panel shown on area 4.
- Measurement option panel: It is used to select a measuring frequency, range mode and range value. The user can select between the Parallel and Series measuring modes as well as between the Tolerance, Relative or Normal modes (modes described in the features section)
- Main display: On this panel the measurements of parameter selected in “Data option” field are shown. Where the Primary parameter is shown with a larger font and the secondary parameter with smaller one. This is a very common practice since by reading values from the display the user can automatically see the most important results.
- Secondary display: On the secondary display the main settings are shown: current selected parameters, measuring frequency and range mode. Also the Min, Max and Average value or Primary parameters are shown.
- Logging table: Is used to log and export measured data. Logging is started by selecting the “Log data” button.
- Option buttons field: I used to manipulate with the table. The “Clear Min/Max” button will reset the Min and Max value on the Secondary display.
220.127.116.11. Connecting the LCR module¶
The main features of the LCR meter applications are described below:
|STEMlab 125 - 10||STEMlab 125 - 14|
|Measured primary parameters||Z, L, C, R||Z, L, C, R|
|Measured secondary parameters||P, D, Q, E||P, D, Q, E|
|Selectable frequencies||100Hz, 1kHz, 10kHz, 100kHz||100Hz, 1kHz, 10kHz, 100kHz|
|Impedance range||1 Ohm-10 MOhm||1 Ohm-10 MOhm|
|DC bias||0.5 V||0.5 V|
|Max input voltage||0.5Vpp||0.5Vpp|
|Parameter range Z||1 Ohm-10 MOhm||1 Ohm-10 MOhm|
|Parameter range Rs, Rp||1 Ohm-10 MOhm||1 Ohm-10 MOhm|
|Parameter range Ls, Lp||100nH-1000 H||100nH-1000 H|
|Parameter range Cs, Cp||10pF - 100 mF||1pF - 100 mF|
|Parameter range P||± 180 deg||± 180 deg|
18.104.22.168.1. MEASURED PRIMARY PARAMETERS: Z, L, C, R¶
LCR meter application will enable you to measure basic parameters of the passive electrical components: R – resistance, C – capacitance, L – inductance and Z – impedance.
22.214.171.124.2. MEASURED SECONDARY PARAMETERS: P, D, Q, E¶
Alongside main parameters the secondary parameters are also measured and calculated. These parameters are common in describing the properties and the quality of the passive components. P – phase of the impedance (phase between current and voltage on measured component), D – dissipation factor (often used to quantify the quality of the capacitor), Q – quality factor (often used to quantify the quality of the inductor), ESR – equivalent series resistance
126.96.36.199.3. SELECTABLE FREQUENCIES: 100HZ, 1KHZ, 10KHZ, 100KHZ¶
LCR meter enables measurements at 4 different frequencies (100Hz, 1kHz, 10kHz, 100kHz). The user can select desired frequency and the LCR application will use sine signals with the selected frequency to measure the impedance.
188.8.131.52.4. RANGE MODES: AUTO, MANUAL¶
Since the measured values are unknown, the LCR meter will adjust the measuring range providing the best accuracy. If the user expects some value in creating ranges, then the Manual mode can be used.
- Measurements modes: Tolerance, Relative, Normal The “Tolerance” and “Relative” buttons are used for measuring in the Tolerance and Relative mode. When deselected, the LCR meter measures in the Normal mode.
- Tolerance mode: the last value measured before clicking the Tolerance button is saved and used to calculate the percentage difference between the new value and the saved one.
- Relative mode: the last value measured before clicking the Relative button is saved and used to calculate relative difference between the new value and the saved one. Equivalent Parameters calculation circuit: Parallel, Series The Parallel and Series measuring modes refer to using the Series or Parallel equivalent circuit for the parameters (R, C, L…) calculation from the measured Impedance Z *. LCR meters will only measure Z as the complex value Z=|Z|e^(jP) where P is the measured phase and |Z| is the impedance amplitude. All other parameters are calculated from the Series or the Parallel equivalent circuit.
- Export of measured data in .csv format
- Min, Max, Average measurements
- 1000 logging points
2.1.6. Console application¶
Lcr meter can be used from console.
root@rp-f01c35:~# lcr Too few arguments! LCR meter version 0.00-0000, compiled at Fri Aug 14 03:29:10 2020 Usage: lcr [freq] [r_shunt] freq Signal frequency used for measurement [ 100 , 1000, 10000 , 100000 ] Hz. r_shunt Shunt resistor value in Ohms [ 10, 100, 1000, 10000, 100000, 1000000 ]. If set to 0, Automatic ranging is used. Automatic ranging demands Extenson module. Output: Frequency [Hz], |Z| [Ohm], P [deg], Ls [H], Cs [F], Rs [Ohm], Lp [H], Cp [F], Rp [Ohm], Q, D, Xs [H], Gp [S], Bp [S], |Y| [S], -P [deg]
For run the lcr, you need to do 23 steps:
) Load the FPGA image of streamingroot@rp-f01c35:/# cat /opt/redpitaya/fpga/fpga_0.94.bit > /dev/xdevcfg
) Launch a console application.root@rp-f01c35:~# lcr 100 100000 -v Frequency 100 Hz Z 5.424000 kOmh Phase 1.364216 deg L(s) 205.533997 mH C(s) -12.324000 uF R(s) 5.422000 kOmh L(p) 0.000000 H C(p) 0.000000 F R(p) 5.425000 kOmh Q 0.023815 D -41.991112 X_s 129.141129 G_p 0.000184 B_p 0.000000 |Y| 0.000184 -P_Y -1.364216 deg