1- laboratory work determination of errors of measuring instrument the Purpose of the work

The content of the work
1. To get acquainted with the structure and operation of devices for magnetoelectric, electromagnetic, electrodynamic systems.
2. Connect the voltmeter to the circuit and determine their error using standard instruments.
3. Get acquainted with the technical data of the voltmeter being tested and write them in the table.
4. Based on the values obtained from the experiment, determine the absolute, relative and induced errors of the voltmeter on the second point.
Wiring diagrams

1. Check the voltmete

2. Measuring the resistance of a voltmeter
Characters in the scheme: V_0, – exemplary vоltmеtr V_x, – being checked vоltmеtr mA – milliammeter; R₁, R₂, R₃ – rheostats with handles; PT- voltage reducer 220/12 V.
Job description and instructions
1. The tool pointer is set to zero using a corrector.
2. The appliance must be used at rated current for 15 minutes before testing.
3. Only the grade values of the instrument should be checked.
4. Checks are carried out first in the process of increasing the voltage, and then in the values obtained by decreasing.
5. When measuring the resistance of a voltmeter, take at least three values and calculate their arithmetic mean.

6. 
   when drawing a curve, the correction value is set along the ordinate axis and combined with the straight line.
   

Table 1

Measure

Ux

U0^'

U0^"

U0o‘r

^'

^"



k





¹

V

increase

V

decrease

V

V

V

V

%

%

%

V

Table 2

Measure	U0		IV			RV	RVo‘r	PVH
¹	bo‘l	V		bo‘l	mА	Ω	Ω	W

Check the ammeter
a) Assemble the diagram shown in Figure 1.2.
b) Connect the circuit to the source and change the A_X from 1 A to 6 A using the rheostat R_n and record that it shows An after every 1A.
v) Change the reading of Ax through the rheostat Rn from 6 A to 1 A and write that it shows A_N after each 1A.
g) Calculate the errors based on the measurement results.

1.3-table

№	IX	IN(increase)	IN(decrease)	Δ(increase)	Δ(decrease)	γ	γ (variation)
	A	A	A	A	A	%	%
1
2
3

Ampermetr qarshiligini o'lchash.
a) To measure the resistance of an ammeter, assemble the circuit given in Figure 1.2 and connect the millivoltmeter mV parallel to the ammeter Ax in this circuit.
b) Using an R_n rheostat, transmit a current of 4-5 different values from the ammeter Ax and record the results showing Ax and mV.
v) Calculate the errors based on the measurement results.
1.4-table

№	IX (A)	U (mB)	RA (Om)	PA (Bt)
1
2
3

Characters in the table
U_x, – display of the instrument being tested;
U'₀ - values when the values of the sample instruments are increased;
U₀^" – the values of the sample instruments when the values are decreasing;
U_0o‘r – the average values of the sample instruments;
I v, – milliammeter show.
6. Calculation formulas
1. Absolute error of voltmeters when increasing and decreasing readings. , .

2. 
   Maximum relative error of the voltmeter
   

, .
3. The highest relative error of the voltmeter
.
4. Voltmeter display variation
.
here U_Xnom – the upper limit of the voltmeter.
The range of measuring instruments is determined as follows:
γ_var = ∆X∕X_inc∙100%= (X_mid−X_decr) ∕ X_inc∙100%
X_inc and X_decr are the largest differences in the ascending and descending values of the measured quantity.
X_inc - the maximum value of the measurement size.
5. Correction
.
6. Voltmeter resistance
.

7. 
   Nominal power consumption of the voltmeter
   

.
Control questions
1. What do you mean by measurement errors?
2. What are the causes of measurement errors?
3. What are the types of measurement errors?
4. What are the values of the resistance of voltmeters?
5. How to connect a voltmeter to a circuit?
6. What is the formula for determining the internal resistance of a voltmeter?
7. What do you mean by correction?
8. What are the absolute, relative and cited errors
9. How to determine the tool display bay
10. What resistances should an ammeter and voltmeter have and why
11. What types of ammeters and voltmeters are available?
12. How to expand the measuring range of ammeters and voltmeters
13. What is the cause of the error in electrical measuring instruments?