Emerson MICRO MOTION 2700 Instalační manuál stáhnout pdf (Strana 71)

Transmitter Configuration and Use: Series 1000 and 2000 Transmitters 61

Required Transmitter Configuration continued

Required Configuration Optional ConfigurationUsing the TransmitterFlowmeter Startup

6.6.3 Configuring the maximum pulse width

The frequency output maximum pulse width defines the maximum duration of each

pulse the transmitter sends to the frequency receiving device, as shown in

Figure 6-9.

Figure 6-9 Pulse width

The pulse width is configurable to values between 0 and 277 milliseconds.

As the frequency increases, at some point the pulse width will become equivalent to the desired output

frequency. This frequency is called the crossover frequency, and is calculated as follows:

Note: Although you can set maximum pulse width to 0, it is not useful because it will result in an

undefined crossover frequency.

At frequencies above the crossover frequency, the output changes to a 50% duty cycle as shown in

Figure 6-10.

Figure 6-10 50% duty cycle

Example

Maximum appropriate flowrate (TV rate factor) is 2000 lbs/min.

Receiving device is configured for 10 pulses/pound.

Solution:

Configuration:

• TV frequency factor = 333.33

• TV rate factor = 2000

FrequencyFactor

Rate

------------

N×=

FrequencyFactor

2000

-------------

10×=

FrequencyFactor 333.33=

• Model 1500 AN

• Model 1700 AN

• Model 1700 IS

• Model 2500 CIO

• Model 2700 AN

• Model 2700 IS

• Model 2700 CIO

Pulse width

Crossover frequency

2 max pulse width×

----------------------------------------------------=

1 2 ... 66 67 68 69 70 71 72 73 74 75 76 ... 263 264

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