Hi Carl,
Thank you for writing in.
The working voltage of the meter is 5V, so if the power supply is 12V you need to step it down.
Here the PDF file is the DATASHEET of the product:
DATASHEET_100080
Hope this can help you.
Best regards

Hi Timothy ,
Thank you for writing in.
Sorry that we do not have a product can meet your demand.
And we are sure where you can find, maybe you can try to search some keywords on Amazon to find it.
Hope this can help you.
Best regards

Hi Luis Bianchi,
Thank you for writing in.
This problem may be caused by that the output voltage and current of the solar panel is not stable standard DC voltage current.
Frequent power-off or step down voltage will cause the data confusion.
Could you Please try to calibrate the meter?
Here is the instruction of calibration:
1. Disconnect the power supply.
2. Short joint calibration point(open the bottom cover, there are two holes on the edge of the circuit board which is marked “W” ).
3. In the mean time, connect to 20V/1A standard DC voltage and current.
4. If the screen displays CAL—,then —PASS that means the calibration is successful, otherwise, it fails.
5. After successfully calibrating, disconnect the calibration point, power the meter again then it can work normally.
Hope this can help you.
Best regards

Hi Ralph Volpi,
Thank you for your reply.
Here the PDF file is the Datasheet of the product.
DATASHEET_090410
Hope this can help you.
Best regards

Hi Clark,
Thank you for writing in.
Wiring instruction:
Red: Power Supply +
Black: Power Supply -, Measure –
Green: Measure +
As your description, there is transformer in your application, so you can connect the red wire to the positive side of the transformer output (please note that the out voltage range should be within 7-30V, otherwise the meter will be burnt).
Hope this can help you.
Best regards

Hello Dudeguy21,
Thank you for writing in.
Could you please tell us more details of the operation, such as the input voltage/current, the wiring, the working environment?
If you can, we sincerely hope that you can send us some images or video to let us check the problem details.
If you do not know, how to upload the images here, you can send us an email (service at droking dot com) with the information.
Looking forward to hearing from you.
Best regards

Hi Joseph,
Thank you for your interest in our product.
Here are two recommendations for you:
Part number: 091016
DROK® DC-DC Step-down Constant Current & Voltage Converter 4-38V to 1.25-36V 12V/24V Buck Voltage Regulator 5A 75W High Power LED Constant Current Driver Module for Lithium Battery Electromobile Charging
Parameter:
Frequency: 180KHz
Weight: about 25g
Input voltage: 4-38V
Output power: 75W(Max)
Transfer efficiency: 96%(Max)
Output current: adjustabel;5A(Max)
Input reverse connection protection: NO
Working temperature: -40 to +85 Celsius
Output voltage: 1.25-36V constantly adjustable
Short-circuit protection: YES(limited current of 8A)
Over-temperature protection: YES(item will stop output atomatically)

Note:
please strengthen cooling when buck converter module is used in more than 3A,35W

Product functions:
1.Work as high-power LED constant current driver module
2.Work as buck converter module with over-current protection
3.Charger of batteries(eg. nickel-cadimium or nickel-metal hydride battery, lithium batteries);can be used in solar panel/wind turbines/etc

Part number: 180051
DROK® Numerical Control Voltage Regulator DC 5-32V to 0-30V 5A Buck Converter, 24V 12V to 5V Step Down Power Converter Adjustable Digital Control Voltage Reducer with LED Ammeter Voltmeter Display
Technical Parameters:
Input Voltage Range: 5-32V (not to over 32V, or it will be damaged)
Output Voltage Range: 0-30.0V (step-down mode, the input must be at least 1V higher than output)
Output Power: 30W max
Output Current: 0-5A (if over 2A, should enhance heat dissipation)
Output Voltage Setting Resolution: 0.1V
Output Current Setting Resolution: 10mA
Power / Load Effect: CV < 20mV, CC < 30mA Voltage Measure Accuracy: ± (1% + 1 digits) Current Measure Accuracy: ± (1% + 2 digits) Dimensions: 75 * 43 * 12 mm Function Mode: 1, Setting Mode: In this mode, you can set the output current and voltage. Press the "SET" button, the digits on the screen will flash, then short press the "-" button to reduce the value, or short press the "+" button to increase the value and long pressing it, the value will increase rapidly. Press the "SET" button again to move to high-digit, move one digit with per pressing. When the setup is completed, press the "ON / OFF" button to determine the set data. At the same time, the system will save the set data to the chip's internal memory. It will also retain the set data when power-up again. 2, Working Mode: This mode is the normal operating mode, only in working mode, you can switch the input and output voltage display. 3, Automatically Output When Power On Function When power off, press ON/OFF button, then supply power to the module. At this time, the monitor will display "-F1-,-ON-", which means the module will output automatically when power on. With the same operation, if the monitor display "-F1-,-OFF-", which means the function, automatically output when power on, is turned off and you need to press the ON/OFF button if you want an output when power on. Hope this can help you. Best regards

Hi chris,
We have checked that there is something wrong with the datasheet.
Here is the correct version for you
090089_DATASHEET
Sorry for the inconvenience caused on you.
Beg your forgiveness and understanding.
Best regards