Voltcraft WBM-460 (CEM DT-9889) Thermal Multimeter teardown by Fraser - Page 1
Forum section: electronics / general

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 12:04:51 am
content: I recently purchased a Voltcraft WBM-460 that was described as "Defective" by its German surplus equipment seller. The unit is a combined True RMS Multimeter with many functions and a thermal imaging camera. The multimeter section of the unit is a serious bit of kit, unlike that found on some low priced thermal multimeters. The thermal imaging section of the unit is quite humble, but very useable, with a resolution of only 80x80 pixels and a frame rate of 50fps. The microbolometer is the ULIS Micro80P module that is illuminated with a decent sized 21 degree FOV lens. Focus adjustment is not provided on the exterior of the multimeter, but is possible once the lens assembly is removed from the multimeter casing.I shall not go into detail about the thermal multimeters specifications here as they are easily found using Google. The unit is actually a product of CEM and is the DT-9889 model in disguise. CEM provide this same unit to several companies for sale under theri brands. Radio Spares even sell it under their name. The Voltcraft WBM-460 is a CONRAD Electronics supplied unit and costs around 550 Euros.https://www.conrad.com/en/p/voltcraft-wbm-460-ir-camera-multimeter-combo-20-up-to-260-c-120-x-120-pixel-50-hz-1661486.html?srsltid=AfmBOopL3ItiAlYKS5652v0fWNZKfnZBhf0JdsLwTvIVeEr8NTWWWIom&refresh=trueUpon testing my 'as new' cosmetic condition WBM-460 I found no fault with it. Further testing revealed an intermittent fault in the voltage measurement mode. The input appeared to go open circuit if the meter was knocked. Suspecting a dry solder joint somewhere in the voltage input circuit, the unit was disassembled and inspected. The fault was quickly traced to the 10 MOhm input pin (1) of the Caddock resistor network. The pin had separated from the ceramic substrate but thankfully the solder pad remained intact. A quick clean-up and resoldering of the pins where they join the ceramic thick film circuit and all was well again. I suspect that the meter had either been dropped or the resistor network pin was a dry joint on the ceramic substrate pad from new. Once the repair was completed I documented the interior of the unit to share here.I am providing pictures of the units internal parts but will not provide a commentary on the parts as I have limited time available.EnjoyFraserNote: In the attached pictures the multimeter is measuring a battery whilst also displaying an image of my coffee mug. Any multimeter function may be selected to share the screen with the thermal image.

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 12:08:30 am
content: Teardown pictures begin.....

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 12:12:27 am
content: Teardown continued........

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 12:16:11 am
content: Teardown continued......

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 12:20:18 am
content: Teardown continued......

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 12:22:03 am
content: ULIS Micro80P microbolometer....

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 12:25:12 am
content: Teradown continued.....Just the FFC shutter assembly and the housing that contains the laser pointer and LED torch.That's all folks !Fraser

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 01:36:25 pm
content: Just some follow-up comments while I have a spare moment.The battery that is used in the WBM-460/DT-9889 is proprietary, which is a pity. Whilst it’s dimensions are similar to some camcorder batteries, the contact format and positioning is non standard. It would be feasible to adapt a standard camcorder battery, such as the common JVC BN-V607U, by adding a suitable contact assembly on the end of the battery (there is room for this).The WBM-460 is NOT equipped with a Bluetooth module. The PCB pads for it are clearly visible on the main PCB. Whether this feature would be a available when the correct module is fitted is not known. A firmware setting may need to be changed. It is a pity that this feature is absent from my unit, but not a deal breaker for me. I shall try to establish which radio module is used in the CEM DT-9889. They are inexpensive so it may be worth some experimentation.The 80x80 pixel resolution and 100mK sensitivity are limiting factors when thinking of using this thermal multimeter for modern micro electronics. It would be more useful when imaging power electronics and electrical installations. The stated minimum focus distance is 0.5m but a ZnSe close-up lens would provide the necessary close range observation capability for PCB observation.This thermal multimeter has plenty of standard multimeter functionality, including thermocouple temperature, frequency (10MHz), Duty cycle, capacitance, current clamp, diode test and a useful 600uA range (0.1uA resolution). The continuity mode is very fast in its response which is useful when carrying out point-to-point PCB track tracing. The display is stated as being a colour TFT type and it is very easy on the eyes…. ExcellentCharging the Li-Ion battery is a PITA as you have to remove it from the meter and it is housed behind a gasket sealed door that is not that easy to open without a large bladed screwdriver for the locking mechanism. I do not know why there is not an external charger port on the meter or charging via the meters 4mm sockets (as found on some Keysight/Agilent multimeters). This battery charging hassle is not welcome and is, IMHO, a design flaw.The microSD memory card is located behind the Li-Ion battery in the sealed battery bay. This is not convenient for the user as the sealed battery compartment cover and battery have to be removed before access can be gained to the card fir download of images to a PC. This is another design flaw as the non-Bluetooth version of this thermal multimeter has no other way to transfer its saved thermal images and measurement recordings.I noted the presence of a USB-C socket on the main PCB and there is a hole in the rear case of the meter, in the battery Bay Area. The purpose of this USB port is not currently known and it’s presence is hidden using the battery bay label. It could be for factory use or some optional data link, but it is blocked by the Li-Ion battery so not very accessible ! It cannot be used to charge the main battery as that battery has to be removed to gain access to the socket ! This socket is currently a mystery but I may investigate further.Would I pay over £500 for this particular thermal multimeter ? It is a NO from me. It does not offer me enough advantages over my other professional multimeters to justify that level of expenditure. I have plenty of options for good thermal imaging and the Infiray P2 Pro would make a far better choice for many users than the low resolution of the WBM-460/DT-9889. I paid 120 Euro’s for my faulty WBM-460. For that money, it is a very nice, useful multimeter with data logging capabilities and a useable thermal imaging camera. I must say that I really like the nice clear multimeter displayFraser

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 01:51:07 pm
content: Whilst searching for the FCCiD of the thermal multimeter I stumbled upon a video by “our” Mike of this forum. He reviewed a CEM produced Bluetooth multimeter and that unit has a battery that is recharged via the 4mm sockets using an adapter. This is what should have been done on the DT-9889. I wonder why they changed to the battery removal for charging strategy ?https://youtu.be/nhOvLISdlKk?si=Y-4YN8HoRlZyNVJlFraser

author: Fraser
author_rank: Super Contributor
timestamp: November 12, 2024, 02:16:47 pm
content: It would appear that the Bluetooth IC used in these CEM multimeters is the Texas Instruments CC2541 simple link device.Fraser