Measurable frequency range 1Hz-5OMHz  Measurable signal frequency up to 30V  Automatic range conversion, no need to manually switch It is DIY soldering project kit , need assemble by yourself. suitable for develop skills for welding learning. Product Name: PIC Digital Frequency Meter Supply voltage: DC5-12V or 9V battery Appearance size: 80mm*60mm*25mm Weight: 80g Feature: 1. Measuring range 1hz - 50Mhz  2, 5 digits display  3. Automatic range conversion, each range has different gate time  4. You can choose the programming mode to set the frequency offset, plus or minus a specific frequency. There are five built-in frequencies in the program, 455.00Khz, 3.9990Mhz, 4.1943Mhz, 4.4336Mhz, 10.700Mhz, which can be directly used for setting.  5. Built-in oscillator circuit and external crystal oscillator to be tested can measure the oscillation frequency of most commonly used crystal oscillators.  6. The power saving mode can be set. In the power saving mode, the frequency measurement value does not change significantly within 15 seconds, and the display screen will automatically turn off. Instruction: ProG: Press and hold the programming button to display ProG, release it to enter programming mode.  Quit: Set without any modification, exit programming mode.  Add : Save the previously measured frequency displayed on the display, and add this value to the frequency measured later.  Sub: Save the previously measured frequency displayed on the display, and subtract this value from the frequency measured later.  Zero: Set the frequency offset value to 0, the displayed value is the actual measured value of the frequency, and the previously set frequency offset value is deleted  Table: You can select the preset frequency offset value in the table. The data in the table is stored in the data EEPROM of the PIC microcontroller. Short press the programming key in the Table state to call up the five built-in offset frequencies 455.00Khz, 3.9990 in turn. Mhz, 4.1943Mhz, 4.4336Mhz, 10.700Mhz, select the desired frequency, long press the operation key to confirm, and return to the main menu, and then operate to select plus or minus to change the frequency offset value.  Psave /NoPSv: Enable or disable the power saving function. In programming mode, the screen displays Psave, the frequency meter is in power-saving mode, long press to switch to non-power-saving mode and exit, display NoPSv is non-power-saving mode, long press to switch to power-saving mode and exit. In the power saving mode, the frequency measurement value does not change significantly, the display will turn off after 15 seconds, and then it will be tried for a short period of time as a reminder. In the frequency measurement range of 3-4Mhz, when the frequency changes by tens of hertz, the display will turn on again, and the power-saving function will be cancelled.