UNI-T UT612

The UNI-T UT612 is a 20000 counts, dual-display, LCR meter with USB/HID connectivity.

See UNI-T UT612/Info for more details (such as lsusb -v output) about the device.

Hardware

• LCR meter chipset: Cyrustek ES51919 (datasheet)
• HID USB to UART bridge: Silicon Labs CP2110 (datasheet)

The ES51919/51920 chipset is found in other LCR meters, too. The chipset communicates via UART (TX only).

The CP2110 USB serial-over-HID chip resides on a separate breakout board, and is connected to the LCR "mainboard" via a three wire flying cable. Red(!) is GND, green is the meter's TX signal, yellow is probably Vcc from USB, RX is not connected.

Photos

• 

  PCB, bird's view

• 

  USB breakout, top

• 

  USB breakout, bottom

Protocol

The protocol for the ES51919 was reverse engineered as part of the DER-EE 5000 driver that uses the same chipset. Below is the excerpt from the source code.

Public official documentation does not contain the protocol description, so this is all based on reverse engineering.

Packet structure (17 bytes):

0x00: header1 ?? (0x00)

0x01: header2 ?? (0x0d)

0x02: flags
        bit 0 = hold enabled
        bit 1 = reference shown (in delta mode)
        bit 2 = delta mode
        bit 3 = calibration mode
        bit 4 = sorting mode
        bit 5 = LCR mode
        bit 6 = auto mode
        bit 7 = parallel measurement (vs. serial)

0x03: config
        bit 0-4 = ??? (0x10)
        bit 5-7 = test frequency
                    0 = 100 Hz
                    1 = 120 Hz
                    2 = 1 kHz
                    3 = 10 kHz
                    4 = 100 kHz
                    5 = 0 Hz (DC)

0x04: tolerance (sorting mode)
        0 = not set
        3 = +-0.25%
        4 = +-0.5%
        5 = +-1%
        6 = +-2%
        7 = +-5%
        8 = +-10%
        9 = +-20%
       10 = -20+80%

0x05-0x09: primary measurement
  0x05: measured quantity
          1 = inductance
          2 = capacitance
          3 = resistance
          4 = DC resistance
  0x06: measurement MSB  (0x4e20 = 20000 = outside limits)
  0x07: measurement LSB
  0x08: measurement info
          bit 0-2 = decimal point multiplier (10^-val)
          bit 3-7 = unit
                      0 = no unit
                      1 = Ohm
                      2 = kOhm
                      3 = MOhm
                      5 = uH
                      6 = mH
                      7 = H
                      8 = kH
                      9 = pF
                      10 = nF
                      11 = uF
                      12 = mF
                      13 = %
                      14 = degree

0x09: measurement status
          bit 0-3 = status
                      0 = normal (measurement shown)
                      1 = blank (nothing shown)
                      2 = lines ("----")
                      3 = outside limits ("OL")
                      7 = pass ("PASS")
                      8 = fail ("FAIL")
                      9 = open ("OPEn")
                     10 = shorted ("Srt")
          bit 4-6 = ??? (maybe part of same field with 0-3)
          bit 7   = ??? (some independent flag)

0x0a-0x0e: secondary measurement
  0x0a: measured quantity
          0 = none
          1 = dissipation factor
          2 = quality factor
          3 = parallel AC resistance / ESR
          4 = phase angle
  0x0b-0x0e: like primary measurement

0x0f: footer1 (0x0d)

0x10: footer2 (0x0a)

Resources

• Official UNI-T UT612 related documents (manual, software, ...)
• eevblog.com: Review and tear-down of UNI-T UT612 LCR meter