Traditionally, bypass diodes can only be inspected for good working condition at night or when power is not being generated by the solar panels in order to verify that any applied current is guided past the solar cells. With the FT4310 Bypass Diode Tester, you can detect for open faults even when the sun is out without covering the panels. Also test for short-circuit faults and cell string losses.

Basic specifications (Accuracy guaranteed for 3 years, Post-adjustment accuracy guaranteed for 3 years)

Measurement items Open-circuit voltage, Short-circuit current, Bypass route resistor

[BPD TEST mode]

Measurement items Bypass diode comparator judgment, Bypass route resistor, Open-circuit voltage, Short-circuit current, Measurement (applied) current
Measurement object Crystal system string Open-circuit voltage: 1000 V DC or less, Rated current: 2 A to 12 A DC
Measurement method Short-circuit and pulse voltage application
Measurement accuracy Open-circuit voltage: ±0.2% rdg. ±3 dgt. (at 0 to ±1000 V) Short-circuit current: ±3% rdg. ±3 dgt. (at 0.0 to 15.0 A) Bypass route resistance: ±5% rdg. ±5 dgt. (at 0.0 to 15.0 Ω, During pure resistance measurement)
Measurement time 2 s or less (3 seconds or less when measurement voltage is 10 V or less)
Possible number of measurements 3000 times (Comparator, backlight, Bluetooth® OFF) LR6 Alkaline battery × 6

[Voc mode]

Measurement items Open-circuit voltage
Measurement range 0 V to 1000 V DC (Displayed up to 1200 V DC), Accuracy: ±0.2% rdg. ±3 dgt.
Response time Within 1 sec.


Dustproof and waterproof IP40 (EN60529)
Functions Displays the number of bypass diode measurements, Automatic polarity judgment function, Comparison display, Auto hold, Live circuit indicator, Buzzer sounds, Backlight, Comparator, Battery indicator, Auto power off, Bluetooth® Smart
Interface Bluetooth® 4.0LE, Supports devices: iOS, Android TM smartphone/ tablet
Power supply LR6 (AA) alkaline battery×6, Maximum rated power 18 VA Continuous operating time: 45 hours (Comparator, backlight, Bluetooth® OFF)
Dimensions and mass 152W×92H×69D mm (5.98 W × 3.62 H × 2.72 D in) 650 g (22.9 oz) (including batteries, excluding test leads)

Countries and regions where wireless operation is currently supported (FT4310)Last update: June 26, 2019

Wireless certification Japan, United States, Canada, Austria, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom, Thailand, Chile, and Mexico
Exempt from wireless regulations Viet Nam, Hong Kong, Macao, Myanmar, Russian Federation, Colombia, Pakistan, Peru, Georgia, and Kenya

Key Features

• Test for open or short-circuit bypass diodes even during the day*1

• Easily test using the strings in the junction boxes*2

• Save time – simultaneously measure all electrical parameters*3

• Automatically transfer data wirelessly (Available for Android and iOS devices*4)

Application Notes