!
Q. Can I use my own temperature sensor with
the One Series temperature switch?
A.
No. The One Series temperature sensors are integral to the electrical and mechanical design
of the system. The mechanical bond between the electronics housing, the sensor housing and
the lead wires enables the One Series to meet strict agency approvals. Any deviation in lead wire
size, material and length will induce an offset which cannot be compensated for in the field.
Q. Why are "dry contacts" sometimes preferred
over a solid-state relay?
A.
Historically, solid-state relays were associated with high leakage current and effects from RF
noise and other forms of electronic interference, making dry contacts preferable over early solid-
state relay designs. The One Series utilizes a metal oxide semiconductor field-effect transistor
(MOSFET) output providing extremely low leakage current (<1uA). This design provides an open
drain collector suitable for Division 2, hazardous locations. A mechanical relay, with dry contacts,
is not suitable for Division 2 applications.
Q. Can the One Series optional 4 to 20mA output
be "spanned" or "ranged" at the instrument?
A.
No. The One Series is unlike a process transmitter in this regard. The One Series 4-20mA
output is intended as an auxiliary signal for monitoring the process and process trending. This
output can be easily scaled at the PLC using a simple program. Additionally, One Series option
M205 allows the 4-20mA output scale to be specified during manufacturing.
Q. Is the IAW duty cycle of 25mS an issue
for interfacing with a PLC?
A.
No. Because the One Series is a threshold detection switch, it needs to be fast. If the PLCs
scan rate is <25mS, a simple ladder logic routine or Selectable Time Interrupt (STI) can be
implemented to properly receive the IAW signal.
Q. Is it necessary to re-calibrate the One Series
at regular maintenance intervals?
A.
Within the normal operating range, no! The calibration method used during manufacturing
compensates for temperature differences over the entire operating range of the sensor. This
compensation data (sensor characterization) is stored in the One Series non-volatile memory for
the life of the product. The sensors analog output is digitized and combined with the sensor
characterization data, removing any interpretation errors that could otherwise occur. This method
of individually profiling each One Series makes them resistant to drift or shifts in value over time
and temperature range, eliminating the need for periodic re-calibration.
