The Series 641RM Air Velocity Transmitter with Remote Probe features the same highly accurate heated mass flow sensor as the Series 641, with a remote probe construction. The units 6´ cable which connects the sensing probe with the electronic enclosure allows the enclosure to be mounted where it can be more easily accessed.
NIST CALIBRATION available in Product Configurator.
We have recently replaced a Dwyer air velocity transmitter (PFS1300204) with a Dwyer Series 641. The new sensor works fine for only a few days and then starts reading almost no flow. These devices are used in an Air Scrubber application (exhaust stack). Is this the right application for the Series 641? I suspect that moisture might be the issue, but I cannot confirm.
I do not think you are using the 641 series air velocity transmitter in an appropriate application. Any moisture or particulates in the exhaust could be causing damage to the hot wire sensor, leading to the failure. The difference in the sensors is probably why you got longer life out of the PFS series, which unfortunately, is no longer available. The PFS series used a glass filled polyester sensor, which is a little more robust and can with stand the elements a little better. In your specific application, you might take a look at our 641B series which uses a heated mass flow sensor which can be used in dirty air environments.
Mounting gland. Versatile adapter slips on any Series 160, 5/16" standard pitot tube made after Dec. 1990. Two-part stainless steel fitting slides over tube and provides permanent, secure mounting. Where duct interior is accessible, use the washers and jam nut supplied. For blind applications or in thicker materials, use model A-156 flange mounting plate. Once tube is adjusted to proper depth and angle, tighten smaller hex bushing to lock position. Graphite bushing inside assures leak-proof seal even at higher temperatures. TFE bushing also available. Note: For full insertion with this fitting, order next longer pitot tube. A-159 mounting gland is used for both duct mounting and flange mounting.
Flange mounting plate with 1/2" female NPT.
Split flange mounting. Can be added to any Dwyer® No. 160 standard pitot tube. Cadmium plated steel. Gasket is pattern for mounting holes. Secure flange loosely to tube, adjust tube depth and tighten screws. Gasket of 1/16" Neoprene fits tightly around tube and against duct for leak-proof seal. Nuts, washers included.