Payment Options

Q: What are my payment options?
A: E & M Sales’ standard terms for approved customers are Net 30 Days.  We also accept checks, VISA, MasterCard and American Express cards as well as wire transfers and direct deposits.

E & M Sales

Q: What does E & M stand for?
A: Electrical and Mechanical.

Q: What is Ohm’s Law?
A: Ohm's Law explains the inter-relationship between Watts (W), Volts (E), Amps (I) , and Resistance (R).  Resistance is the one variable which is constant for most resistive heaters.  Watts and current will both change if voltage is varied.  Watts are a result of voltage and current; changing voltage will change current draw and watts. 

Q: What is watt density?
A: Watt density is the rated wattage per unit of the heated surface area, most commonly expressed in W/in2 or W/cm2.

Q: What is CV?
A: The flow coefficient of a device is a relative measure of its efficiency at allowing a fluid flow.  It describes the relationship between the pressure drop across and orifice, valve or other assembly and the corresponding flow rate. 

Mathematically, the flow coefficient can be expressed as:    

 

 

 

Frequently Asked Questions

Q: What is a thermocouple?
A: A thermocouple is a temperature sensing device made by joining two dissimilar metals.  This junction produces an electrical voltage in proportion to the difference in temperature between the hot junction (sensing junction) and the lead wire connection to the instrument (cold junction).
Q: What is an RTD?
A: An RTD (Resistance Temperature Detector) is a sensor that uses the resistance temperature characteristic (the characteristic change in a sensor’s resistance when exposed to a change in temperature) to measure temperature.  There are two basic types of RTDS: the wire RTD which is usually made of platinum, and the thermistors, which is made of a semiconductor material.  The wire RTD is a positive temperature coefficient sensor only, while the thermistors can have either a negative or positive temperature coefficient.
Q: What is an SCR?
A: An SCR (Silicone Controlled Rectifier) is a solid-state device, or thyristor, with no moving parts, that is used in pairs to control ac voltages within one cycle.  SCRs control voltage from a power source to the load by burst firing (also called zero-cross firing) or phase angle firing.
Q: What is an SSR?
A: An SSR (Solid State Relay) is a switching device with no moving parts that completes or interrupts a circuit electrically.
Q: What is a blanket heater?
A: A blanket heater is typically a silicone rubber laminated electrical resistance heater in blanket form.  They are flexible and can be applied to surfaces with different shapes to maintain a process temperature or for freeze protection.
Q: What are the advantages of a silicone laminate heater?
A: Silicone laminate heaters (flexible heaters) can be applied to surfaces of just about any geometry to provide even heating.  These heaters have a low watt density, so they won’t burn the surface or introduce too much heat into a process.
Q: How long will this heater last?
A: This is a common question that does not have a definite answer.  It depends on a variety of factors such as watt density, set point temperature, type of controller, amperage (function of voltage), presence of contamination, shifts per day, as well as many other factors.  The key to making a heater last longer is selection of heater and control.
Q: Can I change the voltage on a valve?
A: Yes.  Most of the solenoid valves we sell have the option to replace the existing coil with a coil of a different voltage.
Q: What is PID control?
A: PID (Proportional, Integral, Derivative) is a control mode with three functions: proportional action dampens the system response, integral corrects for droop, and derivative prevents overshoot and undershoot.