Kingtronics Blog

II. Selection Criteria
The initial considerations for trimmer type selection are:
A. Resolution of adjustment
B. Setability and time to set
C. Physical and environmental conditions
D. Stability of setting required
E. Circuit packaging requirements

A. Resolution of Adjustment
1. Multiturns
• Multiturns provide better resolution than single turns. Models with a longer element exhibit better resolution than those with a short element. Typical multiturn shaft revolutions range from 15 to 20 turns for end to end travel.
• The contact design and stability are important considerations in achieving high resolution. The contact area must be small and the contact must move smoothly in order to provide high resolution. A noisy contact will make accurate setting very difficult.
• All trimmers utilize smooth cermet materials, precious metal wire brush contacts and backlash-free wiper designs that ensure high resolution setability.
• Reference multiturn models:
Square multiturns - 44, 64, 66, 67, 68
Rectangular multiturns 78, 89

2. Single Turns
• Single turn resolution for models with a longer cermet element (larger diameter) is quite respectable. This is especially true with wire brush contacts and smooth cermet films.
• Reference single turn models:
Small diameter - 24, 25, 62, 82
Larger diameter - 72, 91, 93

3. Surface Mount Models
• Single turn - 21, 23, 83
• Multiturn - 44, 84

A trimmer can be used as potentiometer or rheostat. A potentiometer is a three terminal device typically used to vary voltage. In potentiometric configurations, the wiper terminal is lightly loaded so that wiper current is generally small.

A rheostat is a two terminal device typically used to control current. Wiper current is generally larger in rheostat circuits.

I. Types of Applications
The majority of applications for trimmers occur in electronic circuits. 
Typical uses are in the following devices:
A. Amplifiers
B. Timing circuits
C. Voltage and current regulators
D. Voltage and frequency converters

WELDABILITY:
The ability of materials to be welded together under specified conditions.

TERMINAL STRENGTH:
The ability of the terminals to withstand specified mechanical stresses without sustaining damage that would affect utility of the terminals or operation of the trimming potentiometer.

IMMERSION SEALED:
The ability of the unit to withstand submersion in acceptable cleaning solutions used in normal soldering processes without performance degradation under specific environmental conditions.

TORQUE

STARTING (OPERATING) TORQUE:
The maximum moment in the clockwise and counterclockwise directions required to initiate shaft adjustment anywhere in the mechanical travel.

STOP TORQUE:
The maximum static moment that can be applied to adjustment shaft at each mechanical stop for a specified period of time without loss of continuity or mechanical damage affecting operational characteristics.

SOLDERABILITY:
The ability of the terminals to accept a uniform coating of solder under specified conditions.

Kingtronics offers full range of Trimming Potentiometers with our own trademark "Kt" since 1990.
We gain high reputation by our trimpots superior quality and competitive price. We are proud that Kingtronics Trimpot are well-known in the overseas market.

In Jan 2016, we prepared all the key raw materials of Trimming Potentiometers and then handed over to SGS laboratory.
After 1 week testing , we got the positive reply of our potentiometers from SGS company.  Now we would like to share this good news with our Kingtronics faithful customer.
Kingtronics Trimming Potentiometer is your first chosie, and Kingtronics is your best partner.

More details about our RoHS 2.0 Report, please visit below link:
http://www.kingtronics.com/pdf/Trimming-potentiometer-RoHS.pdf

ROTATIONAL LIFE:
The number of cycles obtainable under specific operating conditions while remaining within specified allowable degradation. A cycle is defined as one complete traversal of the wiper over the resistive element in both directions.

LOAD LIFE:
The number of hours at which a device may dissipate rated power under specified operating conditions while remaining within specified allowable degradations.

ADJUSTABILITY:
Defines the precision with which the output of a device can be set to the desired value.

ADJUSTABILITY (OUTPUT RESISTANCE):
The precision with which the output resistance of a device can be set to the desired value.

ADJUSTABILITY (OUTPUT VOLTAGE RATIO):
The precision with which the output voltage ratio of a device can be set to the desired value.

CONTINUITY:
Continuity is the maintenance of continuous electrical contact between the wiper and both end terminals of the resistive element.

SETTING STABILITY:
The amount of change in the output voltage, without readjustment, expressed as a percentage of the total applied voltage.

DIELECTRIC STRENGTH:
The ability to withstand the application of a specified potential of a given characteristic, between the terminals and all other external conducting member such as shaft, housing and mounting hardware without exceeding a specified leakage current value.

INSULATION RESISTANCE:
The resistance to a specified dc voltage impressed between the terminals and all other external conducting members such as shaft, housing and mounting hardware.

POWER RATING:
The maximum power that a trimming potentiometer can dissipate across the total resistive element under specified conditions while meeting specified performance requirements.

CONTACT RESISTANCE VARIATION: (CRV)
The apparent resistance seen between the wiper and the resistance element when the wiper is energized with a specified current and moved over the adjustment travel in either direction at a constant speed. The output variations are measured over a specified frequency bandwidth, exclusive of the effects due to roll-on or roll-off of the terminations and is expressed in ohms or % of Rt.

EQUIVALENT NOISE RESISTANCE: (ENR)
(Wirewound only) Any spurious variation in the electrical output not present in the input, defined quantitatively in terms of an equivalent parasitic, transient resistance in ohms, appearing between the contact and the resistive element when the shaft is rotated or translated. The Equivalent Noise Resistance is defined independently of the resolution, functional characteristics and the total travel. The magnitude of the Equivalent Noise Resistance is the maximum departure from a specific reference line. The wiper of the potentiometer is required to be excited by a specific current and moved at a specific speed.

RESISTANCE-TEMPERATURE CHARACTERISTIC: (RTC)
The difference between the total resistance values measured at a reference temperature of 25°C and the specified test temperature expressed as a percent of the Total Resistance.
Where:
R1 = Resistance at reference temperature (25°C) in ohms
R2 = Resistance at the test temperature in ohms

TOTAL RESISTANCE: (Rt)
The dc resistance between the input terminals with the wiper positioned to either end stop, or in dead band for continuous rotation potentiometers.

ABSOLUTE MINIMUM RESISTANCE: (Rm)
The resistance measured between the wiper terminal and each end terminal with the wiper positioned to give a minimum value.

END RESISTANCE: (Re)
The resistance measured between the wiper terminal and an end terminal when the wiper is positioned at the corresponding end of mechanical travel.
Absolute minimum resistance and end resistance are synonymous for continuous rotation trimmers.

TEMPERATURE COEFFICIENT OF RESISTANCE: (TC)
The unit change in resistance per degree celsius change from a reference temperature, expressed in parts per million per degree celsius as follows:



Where:
R1 = Resistance at reference temperature in ohms
R2 = Resistance at test temperature in ohms
T1 = Reference temperature in degrees celsius
T2 = Test temperature in degrees Celsius