Frequently Asked Questions
For over four decades, Selco Products has served a wide variety
of markets on a strong yet simple foundation of personal service.
Every member of our customer support team is dedicated to one
goal - providing you with knowledgeable assistance, timely response
to special requirements, and prompt delivery of your order.
From prototypes to volume production requirements, we have structured
our service and engineering support operations to provide a
virtually seamless means of meeting your changing needs. Our
products range from thermal measurement and control devices
to panel mounted analog and digital metering instruments to
a wide range of thoughtfully engineered components. We service
OEM and end-user companies with equal ease, delivering a combination
of price/performance benefits and value-added features that
simplify your product selection efforts and enhances your manufacturing
processes.
Our customers range from the Who's Who of HVAC and telecommunications
to food service, process controls, appliances and recording/instrumentation.
We welcome the opportunity to help you, with a unique combination
of knowledgeable and responsive people, quality products and
prompt delivery. Check our site again soon! We will soon be
offering a full online catalog where you will be able to browse
and order all of our products.
Q: What is the standard differential (hysteresis or ΔT) of the 1/2" Disc Thermostat?
A: 30°F (17°C)
Q: Are tighter or wider differentials available?
A: Yes, 9°F
Q: What is the tolerance on opening and reset?
A: Tolerances are as follows:
| 50°F to 249°F (10°C to 120°C) |
| OA |
Open |
+/- 5.4°F |
3°C |
| |
Close |
+/- 10.8°F |
6°C |
| CA |
Open |
+/- 10.8°F |
6°C |
| |
Close |
+/- 7.2°F |
4°C |
| 250°F to 320°F (121°C to 160°C) |
| OA |
Open |
+/- 7.2°F |
4°C |
| |
Close |
+/- 10.8°F |
6°C |
| CA |
Open |
+/- 10.8°F |
6°C |
| |
Close |
+/- 7.2°F |
4°C |
Q: Are 1/2" Discs available in a one shot (one shot
meaning that it actuates once and cannot be reset)?
A: Yes
Q: Can the thermostat withstand vibration?
A: Yes, standard test is 2mm amplitude with a vibration
frequency of 1,000 C.P.M. (Cycles per minute) applied in the
x, y, and z direction for duration of 20 minutes.
Q: Can the thermostats withstand DC voltages?
A: Yes, tested by manufacturing only the following ratings
apply:
| 12 VDC 10 Amps |
30,000+ cycles |
| 24 VDC 7.5 Amps |
30,000+ cycles |
| 48 VDC 4.5 Amps |
30,000+ cycles |
Q: Are the OA and CA thermostats submersible?
A: No, however Selco has the ability to over mold thermostats
so that they are moisture resistant.
Q: How do I know if I need gold contacts?
A: If your amperage is .250 Amps (250 mA) or less. Gold
contacts prevent premature failure due to oxidation of the
contacts at low amperage levels. Oxidation forms an insulation
layer on the contact and low current does not arc enough to
burn off the oxidation.
Q: At what rate of temperature rise will these devices
remain accurate?
A: Devices are tested at 1.8°F (1°C) per Minute
but can see a rate of temperature rise as fast as 10°F
and remain accurate.
Q: Will the thermostat fail open or closed?
A: There is a 90% probability that the thermostat will fail
open.
Q: What is the Mean Time Between Failure (MTBF)?
A: On a case study we estimated approximately 132,000 hours
of operation.
Q: What is an interchangeable thermistor?
A: An interchangeable NTC Thermistor isa highly accurate thermistor with tolerance values that typically range from ± 1°C down to ± .1°C. The term interchangeable describes a thermistor in a system that can be replaced by another thermistor of the same accuracy. View Selco's interchangeable thermistors.
Q: What is a point matched thermistor?
A: A point matched NTC thermistor provides a specific tolerance at a specific temperature point. The temperature point could be at 25°C or at another temperature point. The tolerance typically can be set from ±10° to ± .1°C. View Selco's point matched thermistors.
Q: What is a DO-35 thermistor?
A: A DO-35 thermistor is a highly stable glass sealed thermistor, with axial leads that has a temperature range from -50°C to 250°C. View Selco's DO-35 thermistors.
Q: Does Selco provide custom packaged thermistor probe assemblies?
A: Yes. Selco works closely with our customers to develop custom, application-specific, probe assemblies to solve their temperature sensing problems.
Q: What are life science thermistor probes?
A: These are very tiny thermistor probes intended for use in disposable medical devices, medical equipment, and instrumentation. Available tolerances for Selco’s LS, LSMN, and LSMC thermistors range from ±.1°C to ± 10%. View Selco's life science thermistor probes.
Q: Does Selco offer thin film encapsulated thermistors?
A: Yes. Selco’s TF Series is a thermistor enclosed in Kapton® Polyimide film insulation that is as thin as .020”. It comes in a variety of lengths and tolerances. View Selco's thin film thermistors.
Q: Does Selco offer longer leads and connector options on their epoxy encapsulated, leaded thermistors?
A: Yes. The CS Series can be customized to include customer specified lead lengths and insulated lead wires. We can also assemble a connector as specified by the customer. View Selco's CS Series.
Q. What's a Collet Knob?
A: Click here to download our PDF on Collet Knobs
Q. Should I use a collet knob, or push-on knob, in my application?
A. The type of shaft you are using and your application will
determine which type of knob is best for you.
Collet knobs are only recommended for a smooth, round shaft
(no splines and no flat on the shaft). Collets are a good
choice when a secure fit is important. A tool must be used
to install or remove collet knobs.
A push-on knob can only be used on a splined shaft or a D
shaft. A push-on knob is a good choice when cost savings is
an important factor. Push-on knobs are held on by an interference
fit, which means that they can be installed and removed relatively
easily.
Q. What materials are Selco knobs made of?
A. Nylon – The majority of the collet knobs and push-on
knobs are made of nylon 6, with a matte finish. This material
is stable in the temperature range of –20 degrees C
to +70 degrees C.
Thermoplastic Elastomer – The Soft Touch knobs have
bodies that are made of thermoplastic elastomer, which has
a soft, textured velvet touch. The pointers on the soft touch
knobs are made of a hard polypropylene.
ABS – Many of the set screw knobs are made of ABS.
Thermoplastic – Some of the appliance knobs are made
of thermoplastic and withstand temperatures up to +70°
C.
Thermosetting – The remaining appliance knobs are made
of thermosetting material and withstand temperatures up to
+220°C.
Q. What is your minimum order for knobs?
A. Selco has a $50.00 minimum order. In addition to the $50.00
minimum, certain knobs will have a minimum order quantity.
While Selco does stock many different varieties of knobs,
we are not able to stock every variety. The knobs that we
do not stock usually have a minimum of either 500 or 1,000
pieces.
Q. What is your lead-time for knobs?
A. Many knobs can be shipped immediately from stock. Other
knobs are made to order. For knobs that are made to order,
the lead time can be anywhere from 3 weeks to 8 weeks. Please
call Selco to get an accurate lead time for the specific part
number that interests you.
Applications:
Professional Audio Equipment
Laboratory Equipment
Medical & Dental Equipment
Industrial Equipment
Lighting
Ovens
Food Equipment
Musical Instruments
Q. What Capillary length is available?
A. Standard is 36 inches (915 mm)
Customs can range from 2 feet to 12 feet
Q. We currently use a long bulb and you only have a short bulb in stock?
A. The performance of thermostats with fluid expansion diastats does change with respect to length or diameter of the bulb. The size of the bulb is proportional to the diaphragm and the movement required to actuate the contacts.
Q. How many inches of capillary should I place in the media?
A. Recommended is 2 inches (50 mm).
If less than or more than 2 inches, may vary from actual calibrated set point. Manufacturing calibrates the bulb plus the first 2 inches of the capillary tube.
Q. What type of media is used in testing bulb and capillary thermostats?
A.
From 0°C to 90°C (32°F to 194°F), the media is water.
From 91°C to 400°C (196°F to 752°F), the media is a salt bath.
Q. What is the rate of temperature rise while testing bulb and capillaries?
A. 1°C to 1.5°C (2°F to 3°F) per minute.
Q. At what rate of heat increase is the bulb and capillary most accurate?
A. 4°C (7°F) per minute.
The faster the rate of temperature rise, the less accurate the thermostat will be (another term for this would be Thermal Delay or Thermal Lag).
Q. What is the differential (also referred to as hysteresis) available on bulb and capillaries?
A. Closest is 2°C (3°F to 4°F) on lower temperatures and 9°C (16°F) on higher temperatures. Widest – varies on temperature setting
On 4-40°C (40-104°F) Max. Diff. Is 4-5°C (7-9°F)
On 30-90°C (85-195°F) Max. Diff. Is 9-12°C (16-21°F)
On 50-300°C (120-572°F) Max. Diff. Is 25-30°C (45-54°F)
Q. What type of stainless steel is used on the Bulb and Capillary?
A. 304 stainless steel. Various types of insulation sleeves are also available for harsher environments.
Q. Are there enclosures available?
A. Yes, metal or plastic enclosures are available on special order. Custom powder coated colors and sizes are also available.
Q. What is inside of the capillary tube?
A. The capillary sensor is charged with a special gas. A temperature change causes a pressure change of the charged gas. This change is converted into a travel via the bellows/diaphragm actuated by a mechanical switch.
Q. How many inches of capillary should I place in the media?
A. The sensing part is a minimum of 6 inches (150mm) of the capillary end
Q. Can I mount the thermostat upside down?
A. Yes, the position of the thermostat switch body with respect to the position of the capillary does not influence the function.
Q. What is the differential?
A. Differential means the difference between cut in (ON) temperature and cut out (OFF) temperature. Differential is almost the same at every point from cold to warm.
Q. What is the tolerance?
A. Usually, the tolerance at the calibration point is ±2.7F (±1.5C). The total at the non-calibration point is ±3.6F (±2C)
Q. Does altitude affect performance?
A. Yes, the thermostats are tested at sea level. If the thermostats are tested or installed at higher altitude where the barometer is lower, the operating temperature will be lower. The compensation values depend on the gas used and the operating temperature.
Q. What type of accuracy?
A. Selco/Asahi DPMs offers 0.1% to 0.3% accuracy ±1
digit, depending on the model.
Q. How many digits are available?
A. The more digits the higher the resolution.
4 digits have more resolution than 3 ½ digits. Example,
the outside temperature is 19.99º F, 3 ½ digits
is more than enough for outside temperatures, but probably
not enough for the surface temperature of aluminum used in
the production of commercial airplanes. 19.999ºF may
be more adequate.
Q. What type of display do you offer?
A. Either of the following:
LED, Light Emitting Diode
LCD, Liquid Crystal Display
LCD’s use little power to operate and are the first
choice for digital displays on battery power.
Q. What Range input signals are available?
A. DPM’s monitored a variety of input variables directly
or monitors sensors, which step down the signal to a manageable
level.
Asahi manufactures meters for AC/DC signal monitoring as
well as temperature and other process variables. You can monitor
a variety of signals.
Generally, it is advisable to select the input range closest
to but not less than the input being monitored.
For example, with a signal of 80 Volts, you would need a
200 Voltmeter, because a 20-volt meter could not handle the
high voltage signal. A 750 volt meter would not be necessary;
the 200 volt meter could handle the load and provide one order
magnitude better resolution.
Q. What type of operating power for the meter is required?
A. Selco/Asahi offers meters with all of the below operating
power requirements.
110 (VAC domestic)
220 (VAC off shore)
9-32 (VDC battery or reduction)
Loop (Best to eliminate noise)
Many Power supply options are available. The most common are
110/220 VAC and 9-32 VDC. Loop powered meters derive power
from the 4-20mA loops they are monitoring, requiring only
a small voltage drop. Loop powered systems are ideal for noisy
electrical situations, as the system is closed from external
power lines running to it.
Q. Do you have meters that can be used in a wash down
environment?
A. Selco/Asahi offers meters that are IP66, NEMA 4 splash
proof. In addition, Selco/Asahi offers covers front covers
for 1/8 DIN sizes that are rated IP66, NEMA 4.
Q. Will your meters fit into my current enclosure cutout?
A. Selco/Asahi offers 1/8, 1/32, and 3/64 DIN Size meters
By moving to the DIN Standard of measurement, it has become
easier to measure a panel space and fit a meter. The most
common is the 1/8 DIN, which takes up 96mm x 48mm
or (3.78” x 1.89”) and requires 92mm x 45mm cutout
or (3.622” x 1.77”).
Q. Do your meters offer any type of output?
A. Selco/Asahi meters are available with Analog, Digital,
Excitation or BCD output.
Analog output signals such as 4-20mA or 0-10 V are usually
sent to chart recorders or other simple recording devices.
As the display increases in value, the analog output increases
in value also. For example, 0-100% displays with a 4-20mA
output would have a 20mA when the display indicates 100%.
The output would be 4mA when the display is 0%. Digital outputs
are for communication between the controller and a host computer
or a printer.
BCD outputs, RS232, RS422, and RS485 are examples of digital
outputs.
Excitation outputs are available in most DC indicators and
controllers, allowing you to power DC external transmitters.
This eliminates the need for expensive DC power sources for
2-wire transmitters and active transducers.
Relay Outputs, relays are coupled with set points programmed
in the controller. The meter takes on control functions when
relays are added to the alarm set points. Generally, when
a set point for the signal input is exceeded, a relay will
be triggered. The relay can be used to turn on or off a light,
a process or an alarm indicator.
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