Inputs requiring external resistor/jumper?

[sysint]

I was having a conversation with someone about powered inputs and on the topic I had remembered Circon UHC series had a jumper switch and they guy said with Distech you need to add the external resistor. I think XL800 modules need external resistor... so the question what do the other vendors do?

[control_8]

They are probably talking about converting a 0-20 mA signal to 0-5 volts (w/ 250 ohm resistor), or 0-10 volts (using a 500 ohm resistor). Companies like ALC can handle 0-20 mA inputs, while Novar cannot (need external resistor to convert to voltage).

[miller_elex]

Don't forget ABB Drives D+ and Dcom.

[lontshooter]

Schnider Electric(TAC) needs resistor to convert 0-10v to 4-20ma.
CSI uses resitor to determind hte input value, these are built into the programmable boards.
Distech uses resistors for there 4-20ma input signal.
Distech also has jumper for output of 4-20ma or 0-10vdc
Circon older controllers need the resistors for conversion also.

Lontshooter

[dapper]

KMC uses 'pullup' resistors. Rocker switches on the boards.

[RyanT]

Delta uses dip switches that apply different resistances.

[kontrolphreak]

RyanT,

When did Delta change to dip switches? All the controllers from Delta I have dealt with use jumpers for input/output configuration.

Delta - Jumpers
Reliable - Dipswitch (M1/M2) Jumpers (VAV/Zone/Stat) - Ext Resistor (4-20mA)
tac Andover - Dipswitch
Alerton - Jumpers
Autmoated Logic - Jumpers
tac Xenta - Software IIRC
JCI - Jumpers

kontrol out

[RyanT]

Kontrolphreak,
maybe I'm using the wrong term here. The inputs on all the newer (V3.22 and up) stuff use switches that are a bit larger than a typical dip, but I dont know what else to call them. On the switch, the installer can choose between 4-20, 10k, 5v and 10v.

[justjohnson]

I always setup my inputs for voltage and use an external resistor to convert - 4-20mA signals to 1-5VDC or 2-10VDC (depending on the controller). That way I can troublshoot down the line easier with a meter rather than having to do the stupid put your meter in series with the signal thing....Just my $.02

[sysint]

JustJohnson- Ask yourself which method is more susceptible to inaccuracy over distance? (0-10 or 4-20)

--- now somebody here will tell you I'm just sales... but ignore that guy for now.

[ab8349]

NDIO boards too...

[RyanT]

AHHHH! I'm deleriously tired. Delta uses jumpers, not dips. Not sure where my head was there!

[doodah]

justjohnson - current remains the same over the entire circuit. go with 4-20 for distances. and there are meters that will read 4-20 without getting in series.

[control_8]

JustJohnson- Ask yourself which method is more susceptible to inaccuracy over distance? (0-10 or 4-20)

--- now somebody here will tell you I'm just sales... but ignore that guy for now.

It's true. But it's TECHNICAL sales.

[justjohnson]

now maybe I'm in for a lesson here - but aren't the dipswitch/jumpers on some controllers just adding/subtracting the resistor into the electrical circuit before the A/D converter just like I add an external resistor? All controllers actually measure voltage - even when using a resistance temp sensor - they send out a reference voltage and the returning voltage calculates to a resistance which equals a temperature. I've not had accuracy problems with mA devices with an external resistor at the controller. Now a device that generates a voltage signal at the device over long runs (>200+ feet) I agree with you you get resistance added because of the wire run and your voltage signal is skewed. Perhaps I'm missing something but that's the way I've always done it and I don't have problems with it.

[BACnet]

JJ- You are 100% correct.

Everyone on this board knows that a current signal won't degrade since it's a closed loop system.

Your assumptions about resistors are right on the money- You can add them yourself or switch/jumper them in if the manufacturer spent the extra 15 cents to make the input selectable. Either way there is no difference electrically.

Of course you want to make sure you're using a resistor that's +- 1% or less- Those cheap 5% resistors are never worth it.