Could someone tell me which CHARM model number to use and the associated terminal block needed if I want to connect a 3-wire NPN or PNP inductive proximity sensor?
I found nothing about a NPN or a PNP sensor in the documentation but with a "Discrete Input 24V DC Isolated CHARM" and a "3-wire DI Fused Injected-Power Terminal Block" it seems that could work. If this is the case, I would like the related documentation.
Here is the link for the inductive proximity sensor datasheet: https://www.go4b.com/usa/datasheets/p300-proxswitch.pdf
The inductive proximity sensor model number is P3001V34C.
Regards,
Patrick
The DI 3 wire terminal block does provide for connection of a PNP sensor. The DI CHARM provides the Load in the below circuit, with the three terminals of the Sensor wired to the three terminals of the CHARM terminal block.
The DeltaV 3 wire terminal block draws power and is grounded to the Injected Power distribution in the baseplate.
The PNP device allows the DeltaV Terminal block to provide up to 1 amp at 24VDC to the device from Terminal 2 and to ground the device to DC Common to terminal 3. The signal connects to terminal 2 through the CHARM "load".
An NPN devices would require the DI Isolated CHARM to be wired into the circuit. This could be accomplished with a DeltaV Power CHARM/Fused TB and a DI Isolated with a standard TB.
The Load is the Isolated DI CHARM and it must connect to the 24 VDC source and to the signal terminal of the NPN device. Power can come from DeltaV Power CHARM or external terminal blocks. Since CHARMS are intended to replace marshalling terminals, connecting with the Power CHARM allows that. If there are a significant number of these devices, it would likely be more economical to manage this NPN wiring via some dedicated terminals that facilitate the power distribution
The NPN device creates a high side sense circuit, were a fault to ground of the DI signal wire would be seen as a True state. With PNP, a fault to ground of the signal wire would result in no signal. My preference would be a PNP device given the single CHARM terminal block ease of connection and signal fault behavior.
If the NPN device is NAMUR, the DeltaV DI NAMUR CHARM would allow connection of signal directly to the CHARM and Power CHARM to Power and ground terminals of the device:
The NAMUR signal monitors for Open Circuit, Open Contact, Closed Contact and Short Circuit, setting the status to BAD if there is a wiring fault. Note that the above requires the use of DeltaV 24 V power so that the NAMUR CHARM is referenced to the same Common as the NPN device's power/common.
The compatibility of the device with DeltaV is governed by the power consumption. DeltaV Power CHARMS are rated for 1 amp continuous load. The NAMUR CHARM operations at lower voltage, but also requires the field device to be NAMUR to et the benefits of wire fault detection and avoiding false True signal on Short to ground of signal.
From here, I think one engineers the solution and researches the various components for a satisfactory design.
Andre Dicaire
In reply to Andre Dicaire:
Thanks Andre for your quick answer. Much appreciated. There is, however, something strange in your answer. I thought NAMUR is a 2-wire device like the one below. Are you sure about a NPN device which is also NAMUR?
Thanks!
Regards
In reply to Patrick Loiselle: