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Fluke 179 teardown photos

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rsjsouza:
I tried to find a Fluke 170 series teardown on the web without success, therefore I took some pictures of my Fluke 179 to show its guts... Quite remarkable construction I must say!

Battery compartment. Usual build in several Flukes, but for the price I would have preferred to see brass inserts instead of self-tapping.


Front cover removed. Absolutely fantastic the molded insulation on the rotary switch and surrounding the fuses, leads and battery.


Front view in detail. Note the rotary switch markings and the depth of the holes that house the front button PCB contacts. You cant ask for much more protection...


Back cover with the circuitry removed. Notice the hole for the cal probe (left), shielding and the buzzer.


Rotary switch. Pretty cool the small tip to aid the switch alignment.


LCD and front buttons. The LCD housing is incredibly tough and fitted. The button contacts are different than the typical "opposing forks" design found everywhere else. Not sure how better this is, but maybe the contact area is larger...


Fuses and test lead inputs. If you are like me, at first glance it seems the battery is too close to the ground PCB track, but a few pictures above you can see the cover has a plastic insulation between the two. Ahhhhh... I can sleep in peace!


Bottom side of the fuses and test lead inputs. Large tracks, solid connection to the shielding (the hole on the right) and the only interesting thing I found was the tiny track that crosses between the two pads on the left. Low clearance, maybe?


Bottom side of the digital circuit. The large round thing is the cal button and one can see the quality of the PCB and routing.


(horrible picture). Removing the plastic white cover. The molded plastic circuit cover also uses self-tapping screws. Not a big fan.


This is the bottom side of the rotary switch without the plastic cover. Notice the large ground plane and the interesting tinned ring surrounding two of the five pins of a device.


The molded plastic with the mounted LCD. Not everybody can claim their equipment has such nice level of finishing...


Back side of the LCD display with the zebra contacts. This assembly is incredibly tight (four screws on the corners guarantee that).


The top side of the PCB. Impeccable component selection and solderings.


Digital section. Two backlight LEDs, two custom parts from LT, one AD737 (TRMS-DC converter) and one "off-the-shelf" MSP430F437.


Input protection, battery clip, rotary switch and the (foil?) resistor under the black plastic cover.


The other side, showing the rectifier bridge, the shunt resistor and the two fuse holders (the 11A fuse is in place). I have no idea what is the square copper under the DALE resistor. Calibration point or assembly PCB orientation maybe?


Enjoy!  :-DMM

alm:

--- Quote from: rsjsouza on January 06, 2013, 04:40:09 am ---Fuses and test lead inputs. If you are like me, at first glance it seems the battery is too close to the ground PCB track, but a few pictures above you can see the cover has a plastic insulation between the two. Ahhhhh... I can sleep in peace!

--- End quote ---
I assume the responsible Fluke engineer didn't lose any sleep over it, since the negative lead from the battery connector is most likely directly connected to circuit ground and the common input terminal. Unless you spotted an isolated DC-DC converter somewhere...

rsjsouza:

--- Quote from: alm on January 06, 2013, 05:56:05 am ---I assume the responsible Fluke engineer didn't lose any sleep over it, since the negative lead from the battery connector is most likely directly connected to circuit ground and the common input terminal. Unless you spotted an isolated DC-DC converter somewhere...

--- End quote ---
Considering the battery compartment is completely isolated from the rest of the circuit using molded plastic, I am pretty sure that someone lost some time thinking about this design choice. I personally don't like to see the battery too close to the input terminals in several other multimeters as any high-voltage surge could cause a spark and either ruin the battery or inflict an overvoltage to the equipment (the battery casing is not connected to the negative terminal).

anotherlin:
Really nice teardown !
I own a 179 but I don't want to open it.

rsjsouza:

--- Quote from: anotherlin on January 07, 2013, 10:15:50 am ---Really nice teardown !
I own a 179 but I don't want to open it.

--- End quote ---
Merci beaucoup; before I purchased mine I found mjlorton's excellent reviews below, but he stopped the teardown just after removing the outside plastic case (I would have done the same; it was a loaner). Thus I hope this helps others have a deeper insight on this excellent DMM.

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