Instructions for using existing
AquaCalc 5000s
having the Advanced firmware
(version H1 to H6) 
with the new Standard Rating Table No. 2

Updated December 10, 2001

The following is an updated version of the instructions contained in Chapter 3 - Using Current Meters of the operating instructions for the AquaCalc 5000 using the Advanced (H) (formerly the Professional Series) firmware.

These instructions have been updated to reflect changes in the Standard Rating Tables for the Price type AA and pygmy meters as discussed in the technical Memorandum No. 99.05, released by the The Office of Surface Water, United States Geological Service on June 2 , 1999. Due to the changes in the Rating Tables and associated equations, the default ratings for the Price type AA and pygmy current meters are no longer correct. To accommodate the new rating equations you must create a user-defined meter for each of the new rating tables and use these while measuring. For a discussion of the New Standards click here.

In addition the current version of the firmware cannot accommodate the four decimal place constants of the new equations. These must be rounded to three decimal places, resulting in an average overestimation of the velocity in each vertical of approximately 0.02 percent. A firmware update will soon be available to expand the decimal places and update the default values for the Price type AA and pygmy meter rating equations.

These instructions will not work with the Basic (G) firmware. Please see the instructions for the Basic (G) firmware.

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Using User-Defined / Non-Standard Current Meters

Contents
Overview
Meter Rating Equations
Entering Single Segment Rating Equations
Entering Two Segment Rating Equations
AquaCalc Meter Constants
Setting the Meter Identifier
Step-by-Step Instructions
Rating Table Values

Overview

In addition to the built in current meter rating curves for the default Price AA and Pygmy meters (all existing Advanced firmware, version H1 to H6, has the rating curves for the Standard Rating Table / Equation No. 1), the AquaCalc can store the rating curves for ten additional user-defined and “nonstandard” or custom current meters.

Each of these user-defined meters is automatically given an index number from 0 to 9. The user assigns a unique six digit identifying number to each for easier reference. This ID number usually corresponds to the current meter serial number, and is used to select the user-defined /non-standard meter when setting up a transect prior to measuring.

We refer to this list of meters as the Meter Table. After selecting an index number and assigning an meter identification number, the user enters the five values representing the meter rating curve equation(s) and the intersect, as defined under the previous heading.

These “nonstandard” or custom meters are given an in index number in the AquaCalc from 0 to 9 and the user can store an identification number for each. This allows the user to quickly select the meter being used from a menu.

To use a nonstandard/custom current meter, the user needs to know the “rating curve” or the equation that defines the relation ship between the number of revolutions per second (R) that the cups spin, and the measured velocity.

If you are using a metric meter please see “Setting the Measurement Standard” in the Setting Up chapter.

Meter Rating Equations

As used by the USGS, meter rating curves are either a single or a pair of equations that define the relationship between the number of revolutions per second (“clicks” divided by measurement time) of the current meter cups and measured water velocity. The equation for a single or for each segment of a pair of equations equation takes the form:

Y = m*X + b

or

Velocity=(m*( Revolutions/Second)) + b

where m is the slope of the line, and b is the intercept. Some current meters, such as a Type AA, use two equations: one of which is used for lower velocities, the other for higher. A crossover velocity is also specified. An example of a Type AA Rating Table with the equations is shown below. 

Entering Single Segment Rating Equations
(i.e.: new Standard Rating Table No. 2 - 6/99)

In the new Standard Rating Table No. 2, the equation for a Price type AA meter is:

EQUATION: V = 2.2048 R + .0178

In this equation, R is the revolutions per second (number of clicks divided by measurement time), V is the velocity. The above equation is interpreted as a single segment line.

Velocity= 2.2048 x rev/sec + .0178

User-defined / non-standard current meter rating curves are stored in the AquaCalc as a series of five “constants” that represent the two equations or intersecting lines of a meter rating curve. Only two values are used in a single segment line, but these are repeated and a dummy fifth constant is used.

Constants C1 and C2 correspond to m1, and b1 for the single segment equation.

Due to the way the AquaCalc 5000 handles single segment equations, you must repeat the same values in constants C3 and C4, and place a value of 1.000 in constant C5.

In addition, the current version of firmware can only handle three places after the decimal so all constants must be rounded to the third decimal place.

So for the sample Price Type AA Standard Rating Table No. 2 (6/99) equation used above:

EQUATIONS: V=2.2048R + .0178

The constants to be entered are:

• C1 = 2.205
• C2 = 0.018
• C3 = 2.205
• C4 = 0.018
• C5 = 1.000

Please see the Step-by-Step: Setting Current Meter Ratings below for instructions on entering these constants in a user-defined meter. Values for the equations for pygmy meters are also listed below.

Entering two-segment rating curves
(i.e.: old Standard Rating Table No. 1)

The USGS Standard Rating Equation No. 1 for a Type AA current meter is shown on the Standard Rating Table No. 1 as:

EQUATIONS: V=2.18R + .20(2.200) 2.170R + .030

In this equation, R is the revolutions / second, V is the velocity. The above equation is interpreted as two line segments, with the velocity at which they intersect in parenthesis:

Line 1: Velocity1= 2.180 x rev/sec + .020

for velocities greater than 2.200 the equation is

Line 2: Velocity2 = 2.170 x rev/sec +.030

These equations can be represented as two intersecting lines on a graph as in the following figure

.

AquaCalc Meter Constants

Nonstandard current meter rating curves are stored in the AquaCalc as a series of five “constants” that represent the two equations or intersecting lines of a meter rating curve.

Constants C1 and C2 correspond to m1, and b1 for the first equation respectively and C3 and C4 to m2, and  b2 for the second equation. The constant C5 is the velocity value at the intersection of the two straight lines.

If you are entering a single line equation (as in the new Standard Rating Table /Equation No. 2) Enter the same constants for C3 and C4 as you entered for C1 and C2 (C3=C1 and C3=C2). Enter 1.000 for C5.

So for the sample Type AA equation used above:

EQUATIONS: V=2.18R + .020(2.200) 2.170R + .030

The constants to be entered are:

• C1 = 2.18
• C2 = .020
• C3 = 2.170
• C4 = .030
• C5 = 2.200

Setting the Meter Identifier - METER ID#

After you have selected the meter type you will be presented with the Meter Identifier screen. This screen allows you to record the Serial Number or some other identifying number of the current meter used to measure the stream. Up to six digits including a period and a dash can be entered. Up to ten Non-Standard meters and their constants can be entered into the Non-Standard meter table and identified by a six digit meter ID or serial number including a period and a dash. The Non-Standard meter table is located in the System Setup area.

Press the +/- key and enter your METER ID#. Press ENTER to complete the entry.

Step-by-Step: Setting Current Meter Ratings

Nonstandard meter settings are setup in the System Settings menu.

- Press the Setup (0) key to access the Main Menu.

- Press the 2 (2 = Systm) key to enter the System Setup. 

- Press Enter until the following screen appears:

To view the meters in the Meter Table press the +/- key. This will show the screen:

 

+Chg NEXT MTR 0  Meter ID: 000000

Continuing to press the +/- key will cycle through the 10 nonstandard meter locations numbered 0-9. When you reach the meter index you wish to use Press Enter to edit that meter.

Press the +/- key to edit the Meter ID as shown below. Up to 6 digits including a dash may be entered as the ID #. This meter ID number usually corresponds to the current meter serial number. Press Enter to complete the selection. It is important to give each nonstandard current meter a different ID number. If you do not, you will have difficulty selecting the correct meter settings to use when setting up a transect.

The next screen will request the constant C1, press the +/- key to change or enter this constant. Existing AquaCalc firmware can only handle three places after the decimal, you must round off to three decimal places. Once you have entered the value, press Enter. 

The AquaCalc will prompt you for each of the remaining constants C2 through C5. Enter them as you entered Constant 1 (C1) above. 

If you are entering a current meter rating that has only one segment (such as the new Standard Meter Rating Table No. 2 equations), repeat the values for C1 and C2 in C3 and C4 (so that C3=C1 and C4=C2). Enter 1.000 for C5. See the sections above for a description of single segment meter constants.

After entering all five “constants”, you will now be returned back to the +Set NON STD. / Meter Table screen, press Enter to return to the Main Menu.

Table Rating Values for the Price AA and Pygmy meters

The following table shows the values to be entered for Price type AA and pygmy meters and for the new Standard Rating No. 2 equations and the old Standard Rating No. 1.

Note that you must round the new Standard No. 2 values to three decimal places to accommodate the limitations of the current version of AquaCalc 5000 firmware. An update of the firmware is necessary to allow for four decimal place entries. This results in an error of approximately 0.02 percent overestimation for the velocity values. Please see our Customer Support page discussing the New Standards for more information.