The Fnirsi LCR-P1 Transistor Tester, a Surprising Device (Review)

Fnirsi keeps amazing me. Not only do they spit out test and measurement tools at an impressive pace, but they also try to innovate in the looks department. The Fnirsi LCR-P1 Transistor Tester is the first Fnirsi tool that landed on my desk in 2025. It reminds of some gadget out of a science fiction movie. It is as if the Fnirsi product designer has total freedom and he or she is using it all. Besides its looks, the LCR-P1 has some more surprises up its sleeve. Let’s take a look.
 

 

Remote Control Decoder?

The LCR-P1 is somewhat larger than a credit card and about 15 mm thick. It has a small square graphic color display on the upper right and a slide switch to the right of it. This is the first surprise, as this switch lets you choose between IR decoding and transistor tester. Indeed, in IR decode mode, when you point a remote control at the device and press a button, the tester shows the code it received. This doesn’t work for every remote control, RC5 is not recognized, but NEC codes are decoded.
 

 

The LCR-P1 Has Adapters for THT and SMT

Below the display is a ZIF 2 × 7 test socket. The contacts are labelled in a somewhat surprising way, but this turns out to be quite practical and flexible really. Another surprise here is that you can remove the ZIF socket and replace it by the SMT adapter included in the box. This allows you to test SMT devices. Besides the SMT adapter, the LCR-P1 also comes with three wired springy hooks. You can stick them in the ZIF socket and attach the hooks to the pins of a large component that doesn’t fit in the ZIF socket or that is soldered on a board.

 

Zener Diode Tester

In the middle of the right side sits a large, round Test button. This is also the On/Off button. Below the Test button is a black pushbutton with Zener printed on it in dark grey. When you press it, it lights up red and the display shows “Voltage Regulation Diode.” So, the LCR-P1 can test Zener diodes too? Another surprise. And it works, I tested some Zener diodes up to 22 V (as I didn’t find any higher in my stock), but the LCR-P1 can go up to 32 V (according to the manual).

Below the Zener pushbutton is a small, perforated area, which looks as if it protects a buzzer, but, surprise, they are for the infrared sensor. Actually, the buzzer is behind it too, but on the other side of the board.

Powerbank?

When you look at the backside of the LCR-P1, you might think that it is a 300-mAh power bank, but it isn’t.

 

 

Let’s Try the Fnirsi LCR-P1

When you switch the tester on, it says “Unknown/No Component/Or damaged” with a large question mark. It also shows the ZIF socket’s connections. Insert a transistor and press test. After about five seconds the results are displayed. These consist of the type of device that was detected, a schematic symbol with pin numbers, and some parameters depending on the detected device type.

For a PNP/NPN transistor you get h_FE, V_BE, and I_E. For a JFET it displays the gate voltage V_G for two different drain currents I_D together with a value for I_DSS. A MOSFET is identified with values for V_T, C_G, R_DS and V_F. According to the manual, the LCR-P1 can also test IGBTs, but I didn’t have any.

JFET Testing with the Fnirsi LCR-P1

I tried an old BF245C, which was correctly identified as a ‘Field-Effect Tube (N-J-EFT)’. (Firmware version 1.0.7. The manual also mentions a MIOSTET transistor. Maybe Fnirsi should hire a non-dyslectic translator?) The values displayed were:

I_D = 3.60 mA, V_G = 2.48 V
I_D = 0 mA, V_G = 4.30 V
I_DSS = 1.57 mA
 

These values were quite consistent over several test runs. You would expect a negative value for V_G for this type of transistor, but then again, it says V_G and not V_GS. V_DS is not specified, however, making it difficult to compare these values to the datasheet. I therefore connected an oscilloscope to the drain and source as identified by the tester and observed an absolute maximum V_DS of about 4.5 volts. The values in the datasheet are specified for 15 volts. Testing the BF245C on a breadboard, I found a cutoff voltage of −4.4 volt. To obtain a drain current of 3.6 mA with a gate voltage of −2.48 V, I had to increase V_DS to 8 volts. For a V_G of −4.3 V as measured by the LCR-P1, I measured a drain current of 4.5 µA. Maybe the tester can’t measure such low values?

JFET Pinout Detection

The pinout of the JFET was detected as G-D-S. According to the datasheet, it should be G-S-D. JFETs are symmetrical devices, so the Fnirsi LCR-P1 can be forgiven, but it does require looking up the datasheet to be sure.

MOSFET Testing

An IRL540N was detected as a Field-Effect Tube (N-E-MOS) with pinout G-D-S, which is correct. The measured values I obtained were:

V_T = 2.11 V
C_G = 2.10 nF
R_DS = 0.4 Ω
V_F = 613 mV

Here, V_F is the forward voltage of the body diode. Again, the test conditions are unknown, making it difficult to interpret these values. Compared to the IRL540N’s datasheet, V_T and R_DS are on the high side.

BJT Testing

Bipolar transistors produce three values, but the manual claims more. Germanium types work too. For a GFT43A it found a PNP transistor with an h_FE of 10, a V_BE of 239 mV and an I_E of 119 µA. Here, I_E seems to be a leakage current, but when trying bipolar silicon transistors like the BC337 and BC557, I obtained I_E values of around 2 mA. That is rather high for a leakage current.

Darlington transistors are not supported but some thyristors (SCRs) are as long as they have a turn-on voltage less than 5 V and a gate trigger current below 6 mA. Triacs are not supported.

Diodes

Besides testing transistors, thyristors, Zener diodes and remote controls, the LCR-P1 can also test silicon diodes, normal and Schottky. LEDs work too. However, the OA81 germanium diodes I tried were detected as resistors, even though they tested fine with a multimeter. For diodes, it displays V_F, I_R and the capacitance.

The LCR-P1 Supports Capacitors Too

This suggests that capacitors can be tested too, and this is indeed the case, from 25 pF up to 100 mF. For a 10 µF, 25 V electrolytic capacitor, I obtained values for Vloss (1%), ESR (1.94 Ω) and capacitance (11.4 µF). Interestingly, if you accidentally test a Zener diode without pressing the Zener button, the diode is detected as a capacitor.

 

Inductors and Resistors

Inductors are supported too by the LCR-P1, from 10 µH up to 1 mH. The LCR-P1 measures inductance and series resistance. And indeed, plain resistors can be tested as well but using a multimeter is quicker.

Batteries

Finally, according to the manual, the Fnirsi LCR-P1 can test batteries up to 4.5 V, but that didn’t work for me. After thinking for a long time, the tester showed either a random result like a JFET or a battery with an incorrect voltage. This is not a problem, though, as testing batteries with the device is not very practical anyway. And it is a transistor tester, not a multimeter.

The device switches off automatically after one minute (or after a long press of the Test button).

Conclusion

The Fnirsi LCR-P1 is a small transistor tester full of surprises. Besides testing transistors, it can also test normal diodes and Zener diodes, thyristors, and components like resistors, capacitors and inductors. It can also test batteries, even though that didn’t work very well for me. Most surprisingly though is that the LCR-P1 allows testing common infrared remote controls.

Testing a component is as simple as pressing a button, but it is a bit slow. Also, the test conditions for the various parameters are not specified, which makes it hard to interpret the results. Therefore, the LCR-P1 is best used for comparing or sorting transistors (or other supported components) and finding dead parts.

The LCR-P1 is Low Power

The battery of the Fnirsi LCR-P1 is a small 300 mAh affair, yet it lasts surprisingly long on one charge. There is no battery charge indicator, so I don’t know how much is left after all my experimenting, but I didn’t recharge it once.

A software update correcting some of the strange English would be nice, but I can live without. Let’s say that’s the charm of Fnirsi design (together with the affordability of their products, the LCR-P1 costs around €35).