SenSmart 3000 User's Manual
Document: UM-1003
Revision Level B
6
Relays / RS-485 Modbus Option Board (requires 10-0233 I/O Power Supply and 3-wire
operation): 40 mA per relay (120 mA total with all 3 energized); RS-485 use adds 20mA
Memory:
Non-volatile E2 memory retains configuration values in the event of power outages.
Loop Resistance at nominal 24 VDC power:
650 ohms maximum in 2-wire mode
750 ohms maximum in 3-wire mode.
Relays (Optional):
Three configurable form C (SPDT) relays rated for 5 amp at 30 VDC or 240 ~VAC
RESISTIVE
.
Relay 1 and Relay 2 level alarms are configurable for HIGH or LOW trip, for normally energized
(Failsafe) or normally de-energized and for latching or non-latching.
Relay 3 is always normally energized for failsafe operation so loss of power to the SenSmart
3000
will be indicated as a “FAULT” condition.
CAUTION:
Relays are rated for RESISTIVE loads. Inductive loads, such contactor coils or
motors may cause contact arcing, which emits RFI into the sensor signals. Use appropriate
snubbers and MOV’s across inductive loads and keep wiring away from signal wires.
2.6
Field Wiring Installation
4-20mA Transmission Range Info:
The distance 4-20 mA signals can travel is dependent upon several factors including the cable
gauge, DC power supply voltage level and impedance of the input of the receiving device.
Assuming a nominal 24 VDC power supply, maximum total loop resistance is 650 ohms in the 2-
wire mode.
Note:
ST-71 Controllers have 4-20mA input resistance of 100 ohms.
2.7
SenSmart 2000 2-Wire Intrinsically Safe & Explosion Proof
Installations
SenSmart 2000s equipped with 10-0247 sensor heads are NRTL (Nationally Recognized Testing
Lab) certified as suitable for both intrinsically safe and explosion proof installations. SenSmart
2000s equipped with 10-0247IS sensor heads (XP flame arrestor is not installed to allow
monitoring of highly reactive gases such as chlorine) are NRTL certified as suitable for
intrinsically safe installations. All SenSmart 2000s are NRTL certified for explosion proof
installations as long as the sensor head is CSA certified as explosion proof. Follow instructions
on Installation Drawing # 11-0100 in section 2.7a for correct intrinsically safe installations.
Description:
The 2-wire current sinking transmitter is the easiest and most economical to install since there are
only two wires. All of the power needed comes from the current loop and wire sizes may be
smaller. However, only very low power applications are eligible for such transmitters. The
SenSmart 2000 Display assembly shown in Figure 2-4 consumes <2.5 mA of quiescent current.
Toxic and oxygen electrochemical sensors generate their own signals and therefore require no
additional current. If a 4-20mA output is all that is required for toxic / oxygen measurements (no
LCD backlight, alarms or RS-485) the SenSmart 2000 may be used in the 2-wire mode.
CAUTION
: It is important to understand the receiver, or controller device must supply the loop
power in 2-wire 4-20mA modes. Be sure the receiver to be used supports this type of operation.
Instructions:
Unscrew the cover on the SenSmart 2000 explosion-proof enclosure. Loosen the 2 thumbscrews
holding the display assembly in place and remove it. A small sensor cable is attached with
