Spirax Sarco RIM20, Инструкция по установке и обслуживанию, Страница: 38 / 132

IM-P198-05 MI Issue 2 38
Fig. 30 Isolated 4-20 mA output using meter provided power supply
3.22 Frequency output connections
The frequency output is used for a remote counter. It can be scaled to output a 1 to 10 kHz
signal proportional to mass or volume flow, temperature, pressure or density.
The frequency output requires a separate 5 to 36 Vdc power supply; however, there are
current and power specifications that must be observed.
The output can conduct a current up to 40 mA and can dissipate up to 200 mW. The output
is isolated from the meter electronics and power supply.
There are three connection options for the frequency output-the first with a separate power
supply (Figure 31), the second using the flowmeter power supply (Figure 32)(dc powered
units only), and the third using the internal 24 Vdc power supply (Figure 33)(ac powered units
only). Use the first option with a separate power supply (5 to 36 Vdc) if a specific voltage is
needed for the frequency output. Use the second configuration if the voltage at the flowmeter
power supply is an acceptable driver voltage for the load connected. (Take into account that
the current used by the frequency load comes from the meter's power supply). Use the third
configuration if you have an ac powered unit only. In any case, the voltage of the frequency
output is the same as the voltage supplied to the circuit.
mA meter
For HART
communications
the signal loop
must have a
minimum of
250 ohms load
resistance.
RL
 250 Ohm
4-20 mA +
4-20 mA -
+ 24 Vdc
- 24 Vdc
mA meter
For HART
communications
the signal loop
must have a
minimum of
250 ohms load
resistance.
RL
 250 Ohm
4-20 mA +
4-20 mA -
+ 24 Vdc
- 24 Vdc
dc powered flowmeters only
Fig. 29 Non-isolated 4 - 20 mA output using flowmeter input power supply
ac units only
Flowmeter provided dc power
For HART ®
communications
the signal loop
must have a
minimum of
250 ohms load
resistance
RL ³ 250 Ohm .
For HART ®
communications
the signal loop
must have a
minimum of
250 ohms load
resistance
RL ³ 250 Ohm .