Intro:

The protocol used by the UT61e is quite simple, each packet contains 14 bytes. It constantly streams packets as the screen is updated at around 2 packets a second. The 14 bytes are basically a string where the range, digits, function, status are contained.

The serial interface settings are:

19200 baud, odd parity, 7 data bits, 1 stop bit, no handshake.

Describing the protocol:

This snippet shows you how the data is separated, I handle the 14 bytes as a string, which simplifies the process of separating each portion and since this is a low sampling rate application with low priority, it’s not a resource hog.

If ReadSerialPortData( port, @inp, 14 )
 
	If AddElement( *this\sample() )
		*this\sample()\range 		= Asc(Mid(inp,  1))  ; RANGE
		*this\sample()\digits		= Mid( inp, 2,  5 )  ; DIGITS
		*this\sample()\function 	= Asc(Mid(inp,  7 )) ; FUNCTION
		*this\sample()\status		= Asc(Mid(inp,  8 )) ; STATUS
 
		*this\sample()\option[0]	= Asc(Mid(inp,  9 )) ; OPTION 1
		*this\sample()\option[1]	= Asc(Mid(inp, 10 )) ; OPTION 2
		*this\sample()\option[2]	= Asc(Mid(inp, 11 )) ; OPTION 2
	EndIf
 
EndIf

I believe the last two digits are the “end of packet” limiter (CRLF) however I currently cannot test this, I wrote the code a long time ago and I forgot to comment on this slight detail, but as you can see I’ve defined the CRLF contants, so it must be there.

A list of constants:

Here are some constants from my UT61e (unpublished) library…

#FUNCTION_VOLTAGE 		= %0111011
#FUNCTION_AUTO_CURRENT_UA 	= %0111101
#FUNCTION_AUTO_CURRENT_MA 	= %0111111
#FUNCTION_CURRENT_22A		= %0110000
#FUNCTION_CURRENT_MANUAL_A	= %0111001
#FUNCTION_OHMS			= %0110011 
#FUNCTION_CONTINUITY		= %0110101
#FUNCTION_DIODE			= %0110001 
#FUNCTION_FREQUENCY		= %0110010
#FUNCTION_CAPACITANCE		= %0110110
#FUNCTION_TEMPERATURE		= %0110100
#FUNCTION_ADP			= %0111110
 
#RANGE_ONE			= %0110000 ; Example: 22.000nF
#RANGE_TWO			= %0110001 ; Example: 220.00nF
#RANGE_THREE			= %0110010 ; Example: 2.2000µF
#RANGE_FOUR			= %0110011 ; Example: 22.000µF
#RANGE_FIVE			= %0110100 ; Example: 220.00µF
#RANGE_SIX			= %0110101 ; Example: 2.2000mF
#RANGE_SEVEN			= %0110110 ; Example: 22.000mF	
#RANGE_EIGHT			= %0110111 ; Example: 220.00mF
 
#DIGIT_0			= %0110000
#DIGIT_1			= %0110001
#DIGIT_2			= %0110010
#DIGIT_3			= %0110011
#DIGIT_4			= %0110100
#DIGIT_5			= %0110101
#DIGIT_6			= %0110110 
#DIGIT_7			= %0110111 
#DIGIT_8			= %0111000
#DIGIT_9			= %0111001
 
#STATUS_OL			= 1 < < 0
#STATUS_BATT			= 1 << 1
#STATUS_SIGN			= 1 << 2
#STATUS_JUDGE			= 1 << 3
 
#OPTION1_RMR			= 1 << 0
#OPTION1_REL			= 1 << 1
#OPTION1_MIN			= 1 << 2
#OPTION1_MAX			= 1 << 3
 
#OPTION2_0			= 1 << 0
#OPTION2_PMIN			= 1 << 1
#OPTION2_PMAX			= 1 << 2
#OPTION2_UL			= 1 << 3
 
#OPTION3_VAHZ			= 1 << 0
#OPTION3_AUTO			= 1 << 1
#OPTION3_AC			= 1 << 2
#OPTION3_DC			= 1 << 3
 
#UT_CR				= %0001101
#UT_LF				= %0001010

That’s all for now, I currently don’t have a serial interface to test with (Ain’t got the USB cable either) so I can’t finish the library as to post it, but hopefully I’ll get it done eventually.

The supplied software by UNI-T is pretty bad and it’s Windows only, hence the drive to write my own.

As it is, it should give someone a head-start if they’re about to write their own front-end. On the datasheet of the UT61e controller it’s all explained in fine detail, but I can’t recall the number at the moment.

This whole thing was part of a bigger picture, but I had to give up the concept due to lack of funding.

Alright, enough of this shoulda, coulda, woulda!

Cheers,
Gus

The differences between them are:

• RS232 Interface
• True RMS

How:

Turns out you can enable the RS232 interface by shunting pin 84 to GND, you will then obtain the data through pin 64 which is TX.

Originally pin 64 would drive the base of a PNP (2n3906) which in turn would drive an IR LED, this LED provides optical isolation — Typically there would either be an external plug-in module with a photo-transistor or it would have the module built-in, with the connector exposed to the user.

My suggested modification would only require a small hole at the back of the enclosure to expose the LED, you could then interface with it rather easily.

True-RMS cannot be “unlocked” easily since this feature requires an extra IC (AD737 or similar) which obviously isn’t populated on the C version. Other components around this IC are required as well.

Notes:

I’m not sure but perhaps the quiescent current would increase if you have the RS232 mode enabled, it may be worth testing.

For a protocol specification you may refer to the FS9721 LP3 datasheet, even though it’s in Chinese you should be able to comprehend most of it. Scroll near the bottom to find the RS232 section.

Either way, if you have the UT60C and you wish you had data-logging capabilities, give this a go — You don’t have to make any permanent changes if you only intend to test it.

References:

• FS9721 LP3 datasheet (this is the main IC used throughout)
• UT60E Schematic
• UT60C Schematic