1、ULTRASENSE EDPT & EDPTjrElectronic Differential Pressure TransmitterINSTALLATION & OPERATINGINSTRUCTIONSP.O. Box 465 Garner, North Carolina 27529 TELEPHONE 1-800-656-2004 or 919-779-2004 FAX 919-779-5767ULTRATECH - A Hamlin Company, 1994CONTENTSMOUNTINGPRESSURE CONNECTIONSELECTRICAL CONNECTIONSCALIB
2、RATIONCALCULATIONSMAINTENANCEOPTIONSNOTESWARRANTY electronic differential pressure transmitter.doc ELECTRONIC DIFFERENTIAL PRESSURE TRANSMITTERINSTRUCTIONSMOUNTINGWhen mounting the EDPT it is necessary to place the diaphragm of the transducer in a vertical position. This prevents a possible shift in
3、 ZERO calibration caused by the sagging of the diaphragm due to its own weight.If the EDPT is furnished as a loose instrument in only its own case, which is approximately 3 5/8” x 3 3/8” x 1 5/8”, then it should be mounted with the mounting plate in the vertical plane.If the EDPT is furnished inside
4、 of an additional enclosure supplied by ULTRATECH, the only consideration for mounting is that the enclosure is in its normal upright position. This will ensure the EDPT itself is in the correct position as described above.CAUTION: Make certain that the NEMA rating of the EDPT enclosure is appropria
5、te for the surrounding environment.PRESSURE CONNECTIONSThe EDPT has two barbed fittings for input connections. These fittings are 0.15” outside diameter to accommodate slipping 1/8” flexible tubing over the outside.The differential pressure input to the EDPT is applied here. The high pressure port i
6、s labeled “+”, and the low pressure port is labeled “-“.It is very important that these connections are free of any leaks, as even a very slight leak may be too great for the very low differential pressures typically measured with this device.Make certain that the lines from the transmitter to the p
7、ressure sources are free of debris, oil, water, etc. If the input source is such that moisture may be introduced or condensed in the lines, then the lines should have a slight vertical grade from the process to the transmitter without any low place that may create a U-type water trap.Electrical Conn
8、ectionsThe most common EDPT, with 4-20 mADC output, has two electrical connections. They are 6-32 screws, spaced 3/8” apart. Each space is approximately 5/16” wide.When connecting devices in a 4-20 mADC loop, connect the power supply to like terminals and all other devices to opposite terminals. The
9、n on each device, the positive terminal is closer to the negative on the power supply.If the EDPT is mounted inside of another enclosure by ULTRATECH, there is usually another terminal strip near the top of the panel with the connections clearly marked. In some cases it may be necessary to rely on s
10、ubmittal data or the operation and maintenance manual supplied for the job to read the appropriate terminal labels.In some applications an EDPT with a 4-20 mADC output may be supplied with a resistor or potentiometer to create a voltage drop that converts the milli-amp signal to a voltage signal. Fo
11、r example, a 500 ohm resistor will create a 2-10 VDC signal.The voltage of the power supply should be between 12 and 35 volts DC. The typical voltage is 24 VDC. However, the resistance in the EDPT output loop may require a higher voltage. Use the following formula to calculate the minimum voltage fo
12、r the load resistance:minimum voltage = (ohms + 300)/50If the EDPT has a 0-10 VDC or a 0-5 VDC output, there will be three terminals, labeled “OUT”, “COM”, and “POW”. They should be connected as follows:“OUT” output voltage, positive“COM” output and negative power supply“POW” positive of power suppl
13、yCALIBRATIONTo calibrate the EDPT, it is necessary to be able to measure both the input and the output of the device. As with any calibration, the equipment used as standards for measurement of input and output should be as accurate as possible.For example, a device with 1% accuracy might be used to
14、 prove the correct operation of the EDPT, but to calibrate and test the transmitter to specifications, an accuracy of 0.1% or better is recommended.The calibration should be performed at a temperature near the ambient temperature of the location at which the EDPT will operate.- Connect the appropria
15、te milli-amp or voltage output meter.See Electrical Connections.- Use a tee to connect a pressure source to the EDPT high port and the high port of the input standard.- Leave the low port of the EDPT and of the standard open to atmosphere, provided the standard is in the same room with the test tran
16、smitter.- Apply input pressure of about 50% to 75% of span, and allow the EDPT to operate for at least 30 minutes for stabilization.- With no input pressure, adjust the ZERO (AZ press RED button) on the EDPT until the output reads 4mADC (or 0 volts for voltage models).- Adjust the input standard as
17、necessary to read zero.- Apply input until the input standard reads the full-scale span of the EDPT, and then adjust the SPAN of the EDPT to read 20 mADC (or full voltage output).- There is very little interaction between ZERO and SPAN adjustments, but check until both readings are correct.- Mid-sca
18、le points may be checked if desired. There is no adjustment for linearity, but this check may verify the linearity, hysterisis, and repeatability of the unit. See CALCULATIONS.- For unit with compound range, elevate the ZERO setting. See CALCULATIONS.CALCULATIONSUse the following formulas for calcul
19、ation of input vs. theoretical output:output mA = (input/span) x 16 mA) + 4mAfor EDPT-SRoutput mA = (input/span) x 16 mA + 4 mAfor EDPT no SR If the EDPT is to operate with a compound range (read negative and positive), elevate the ZERO adjustment to read the proper output with no input.EXAMPLE:If t
20、he EDPT is to operate from -0.2 to +0.3” W.C., the span of the unit will be 0.5” W.C. With no input pressure adjust the ZERO until the outputreads 40%, which is 10.4 mA. Since no input pressure is 0.2” W.C.greater than the corresponding input for 4 mA, substitute into the above equation:(0.2/0.5) x
21、16mA + 4 mA = 10.4 mATo calculate airflow when an ULTRATECH airflow measuring station is used with the EDPT, the effective area (area less sensing probes) is on the metal identification tag located near the HIGH and LOW connections on the airflow measuring station. For other models, use duct area or
22、 manufacturers published effective area.Next, since flow equals velocity times area (ft3 = ft/min x ft2), use these equations for flow calculations:CFM = 4005 x (DP) x areageneral equationCFM = 4005 x (mA out -4)/16 x span x area)for EDPT, no SRCFM = (mA out -4)/16 x flowfor EDPT-SRThe above equatio
23、ns assume standard operating conditions for the airflow measuring stations and are usually close enough for HVAC applications. To adjust for conditions which vary the density of the process air, substitute 1097/d (where d=density in lbs/cu.ft) for 4005 in the above equations.Input Differential Press
24、ure MeasuredSpan Full Scale Differential Pressure of TransmitterFlow Full Scale Flow of TransmitterOPTIONSTo tell which options are included with an EDPT, look at the two-letter suffix or suffices in the model number.Several different options are available with the EDPT. However, to keep each copy o
25、f this manual as concise as possible, this copy of the manual includes only those applicable to the unit these instructions accompany.One exception is the optional SQUARE ROOT EXTRACTOR as part of the transmitter. This frequently used option is previously discussed in the CALCULATIONS section. It is
26、 designated by the suffix “SR” and is used to provide a signal that is linear to air flow. That is, the output signal is proportional to the square root of the input divided by the span.AUTO ZERO, option AZThis option eliminates any drift in the ZERO setting of the EDPT that may occur either in the
27、electronic circuitry or in the diaphragm of the transducer.This works in the following sequence:- First it holds the transmitter output signal.- Then it opens a solenoid valve between the HIGH and LOW input lines.- Next the unit automatically adjusts the internal ZERO reading.- Then it closes the so
28、lenoid valve.- Finally the output signal is released to normal reading.Note: The EDPT should be mounted to a grounded plate. If the unit is adjusted in the lab with the plate ungrounded, a zero shift may be present. Be sure that you ground the plate in the lab when a bench calibration is performed.T
29、he ZERO is adjusted by pressing the RED push button.With this option there is a “RATE” adjustment. This is to set how frequently the unit will auto zero. It is adjustable from less than one minute to more than one hour. Turn the pot clockwise to increase the time between auto zero operations.The red
30、 light emitting diode on the EDPT-AZ indicates the Auto-Zero function is in process.It is possible to check for operation of the Auto Zero. The units are shipped with the Auto Zero Rate (AZR) set to a location that we feel will give the best performance of the transmitter. Environmental changes in y
31、our process could require touch up of the rate setting. In most cases, the units will perform an Auto Zero Cycle every 30 to 60 minutes. This is determined by the pressure range of the transmitter. Make a note of the setting of the pot. While the frequency of auto zeroing determines the accuracy of
32、the units over time, the actual time is notsuper critical. As a rule of thumb, unless the unit is below .1” of water, a mid scale to full setting of the pot will be acceptable. If the full scale pressure of the unit is at .1” or below, a more frequent rate is needed. Turn the AZR pot fully counter c
33、lockwise. The unit should Auto Zero on its own in 15 to 30 seconds. If the unit does not, there is a problem with the Auto Zero Circuit and the unit should be returned for repairs.HIGH ACCURACY, option-HAThe high accuracy version of the transmitter is usually selected when the unit is to be used on
34、an application that requires a large flow turn-down, such that the unit must operate near the bottom of its input span with the desire for high accuracy not just as a percent of full-scale but as a percent of reading. This allows for a more precise square root scale with special adjustment capabilit
35、y at the low end.These adjustments have been set by ULTRATECH. It is recommended that the factory be consulted before these adjustments are attempted by other than factory personnel.MAINTENANCEThe EDPT is a rugged and reliable instrument requiring no periodic maintenance except for calibration, whic
36、h may be required, depending upon the application of the device.ULTRATECH does recommend at least a quick check of the operation of the EDPT about once a year. This may be performed as follows:- With no input check the EDPT zero setting.- With a known input check for the proper output signal. For he
37、lp see CALCULATIONS.If this quick check points out a problem, recalibrate or repair as required.NOTES:LIMITED WARRANTYULTRATECH INDUSTRIES, INC., hereinafter referred to as Seller, warrants its products to be manufactured in accordance with its published specifications, and to be free from defects i
38、n material and/or workmanship, for a period of one year from date of shipment.Seller, at its option, will repair or replace any product returned to the factory transportation charges prepaid, which Seller, upon inspection, shall determine to be defective in material and/or workmanship. The foregoing
39、 shall constitute the sole remedy for any breach of Sellers warranty.SELLER MAKES NO WARRANTIES, EITHER EXPRESSED OR IMPLIED, EXCEPT AS PROVIDED HEREIN, INCLUDING WITHOUT LIMITATION THEREOF, WARRANTIES AS TO MARKETABILITY, MERCHANTABILITY FOR A PARTICULAR PURPOSE OR USE OR AGAINST INFRINGEMENT OF ANY PATENT. IN NO EVENT SHALL SELLER BE LIABLE FOR ANY DIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY NATURE, OR LOSSES OR EXPENSES RESULTING FROM ANY DEFECTIVE PRODUCT OR THE USE OF ANY PRODUCT.
