Difference between revisions of "Victor 70C"

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| Middle (2 digits after point)
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| Leftmost (3 digits after point)
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| Unused (always contains 0x04)
| ''Unused (always contains 0x04)''


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| Least significant digit on display.


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| Second digit from right.


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| Second digit from left.


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| Most significant digit.


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Revision as of 13:21, 18 August 2012

Victor 70C

The Victor 70C is a 4000 counts, CAT II handheld digital multimeter with USB connectivity. It is also sold as the EZA EZ-735

See Victor 70C/Info for more details (such as lsusb -vvv output) about the device.

Hardware

Photos

  • Device, front

  • PCB, front

  • PCB, bottom

  • DMM/LCD chip

  • NXP HEF4066BT

  • Microchip TC7660E

  • TI 27L2C

  • LCD

Protocol

The device registers on the USB host as a HID-class device. The protocol payload is 14 bytes of data which can be read from endpoint 1, at no more than 1 Hz.

The 14-byte chunk is somewhat obfuscated. To deobfuscate, subtract the ASCII value of the following string from each of the 14 bytes in turn: jodenxunickxia. Then reshuffle the bytes into different positions, according to the following table:

Original position  0  1  2  3  4  5  6  7  8  9 10 11 12 13
Final position  6 13  5 11  2  7  9  8  3 10 12  0  4  1

The deobfuscated payload is then structured as follows:

Byte Bit Value
0 Unused (always contains 0x50)
1 Unused (always contains 0xb0)
2 Flags
0 Minus
1-7 Unused.
3 Major measurement modes
0 Voltage measurement mode, combined with AC or DC flags in byte 6. In combination with the Diode flag in byte 4, signifies diode testing mode.
1 Current measurement mode, combined with AC or DC flags in byte 6.
2 Resistance measurement mode. In combination with the Continuity flag in byte 4, signifies continuity testing mode.
3 Unused.
4 Frequency measurement mode.
5 Capacitance measurement mode.
6 Temperate measurement mode, in Celcius.
7 Temperature measurement mode, in Fahrenheit.
4 Value factors and extra measurement modes
0 µ (Micro)
1 m (Milli)
2 k (Kilo)
3 M (Mega)
4 Continuity (in combination with resistance mode in byte 3)
5 Diode (in combination with voltage mode in byte 3)
6 Duty cycle measurement mode.
7 unused.
5 Extra flags and value factors
0 unused.
1 unused.
2 Max measurement mode.
3 Min measurement mode.
4 unused.
5 unused.
6 n (Nano)
7 unused.


6 Flags
0 unused.
1 unused.
2 Auto-ranging mode.
3 DC measurement.
4 AC measurement.
5 Relative measurement.
6 Hold mode.
7 unused.
7 Decimal point position
0 No decimal point
1 Rightmost (1 digit after point)
2 Middle (2 digits after point)
3 Leftmost (3 digits after point)
4 unused.
5 unused.
6 unused.
7 unused.
8 Unused (always contains 0x04)
9 Least significant digit on display.
10 Second digit from right.
11 Second digit from left.
12 Most significant digit.
13 Unused (always contains 0xd4)

Resources

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