DMTF transit time flow meter utilizes two transducers that function as both ultrasonic transmitters and receivers. The transducers are clamped on the outside of a closed pipe at a specific distance from each other. The transducers can be mounted in V-method in which case the ultra sound transverses the pipe twice, or W-method in which case the ultra sound transverses the pipe four times, or in Z-method in which case the transducers are mounted on opposite sides of the pipe and the ultra sound transverses the pipe only once. The selection of mounting method depends on pipe and liquid characteristics. When the flow meter works, the two transducers transmits and receives ultrasonic signal amplified by multibeam that travels firstly downstream and then upstream (Figure 1). Because  ultra sound travels faster downstream than upstream, there will be a difference of time of flight(¡÷£ô). When the flow is still, the time difference(¡÷£ô) is zero. Therefore, as long as we know the time of flight both downstream and upstream, we can work out the time difference, and then the flow velocity (V) and flow volume (Q) via the following formula.

    

 

 

V= K*D* dt            
  Where:  V: Liquid velocity
  K: Constant
  D: Distance between the two transducers
  dt: difference in time of flight

1.One obvious advantage of Centre-Insertion Series compared with standard Insertion Series is easy to install. The two transducers are mounted in the same side of pipe line, so even the pipe partially buried underground, it still can be installed in the Centre-Insertion mode.

2.Transducers are easy to locate.
3. compared with standard Insertion Series£¬Centre-Insertion Series is less installation spacing requirement. Its longitudinal space is half of standard insertion series, and almost no transverse space demand.
4. Due to the measuring accuracy is based on radius line average velocity; the Centre-Insertion Series is more accurate than all the types of point insertion flow meters.

5. Standard Series and Explosion-Proof types are available.

Transmitter	Power Supply	(Std) 10-28 VDC @ 2.5VA max.115/230VAC 50/60Hz ¡À15%@ 5VA max. Solar energy
	Velocity	0 ~ ¡À40 ft/s (0 ~ ¡À12m/s), bi-directional
	Display	4 line¡Á16 English letters LCD back lit, can display total flow, flow rate, velocity and meter running status etc.
	Units Rate Totalized	User Configured (English and Metric); Rate and Velocity Display; (FWD, NET, REV or BATCH) gallons, ft³, barrels, lbs, litters, m³,kg
	Output	4~20mA, Pulse, Relay, RS232C or RS485, options: up to 8 GB Data logger, Hart +(4~20mA), Modbus
	Accuracy	¡À2.0% of reading at rates >0.5 m/s
		¡À0.003 m/s of reading at rates<0.5 m/s
	Sensitivity	Flow: 0.001f/s (0.0003m/s)
	Repeatability	0.2% of reading
	Security	Keypad lockout, access code enable
	Transmitter     Size	Std.:242*190*115 Weight: <2.5kg
		Exp: 255*220*110 Weight: <5.0kg
Transducer	Liquid Types Supported	Virtually most any liquid containing less than 2% total suspended solids (TSS) or aeration
	Pipe Range	65mm-4570mm
	Suited Liquid Temperature	Std. Temp. Transducer: -40¡æ~121¡æ High Temp. Transducer: -40¡æ~150¡æ
	Cable Length	Shielded transducer cable. Standard length 20fts (6m). Can be extended to 990fts (300m). Contact the manufacturer for longer cable requirement. Cable should not be laid in parallel with high-voltage power line; neither should it be close to strong interference source such as power transformers.