UNCLASSIFIED
TM-INST-030
FLUKE 15B+ MULTIMETER — COMPLETE CALIBRATION EXAMPLE
DC Voltage, Resistance, DC Current, and Frequency Counter Verification
Prepared by: Mervyn Martin, KO6NNH  •  Merced, California  •  26 May 2026
Amateur Radio / Electronics — Not for commercial calibration use

Project Overview

Instrument: Fluke 15B+ Digital Multimeter Goal: Calibrate all major functions using homebrew methods Budget: $22 (reusing some components) Time: One Saturday (8 hours) Result: Verified, documented multimeter accuracy

Starting Condition

Equipment

  • Fluke 15B+ multimeter (purchased 1 year ago, never calibrated)
  • Voltage references (from oscilloscope project - already built)
  • GPS module (from TinySA project)
  • Basic tools, breadboard

Unknown Status

Never calibrated since purchase: - DC voltage accuracy: Unknown - Resistance accuracy: Unknown - Current accuracy: Unknown - Frequency counter: Unknown

Question: "Is my Fluke within spec after 1 year of use?"

Day 1: Complete Calibration

9:00 AM - Planning and Shopping

Inventory: - Voltage references: Have 2.5V and 5V ✓ - Need to add: 1.225V reference - Precision resistors: Need to buy

Shopping list:

From Mouser Electronics (online order, overnight shipping):
                - LM4040A-1.2: $1.50
                - 100Ω ±0.1% resistors × 10: $5.00
                - 1.00kΩ ±0.1% resistors × 10: $5.00
                - 10.0kΩ ±0.1% resistors × 10: $5.00
                - 100kΩ ±0.1% resistors × 5: $3.00
                - 1.00MΩ ±0.1% resistors × 5: $3.00
                Total: $22.50 + shipping

Waited for overnight delivery...

Saturday 9:00 AM - Parts Arrived, Begin Calibration

Package received: - All components arrived ✓ - Quality check: All parts correct

Part 1: DC Voltage Calibration

10:00 AM - Build 1.225V Reference

Circuit (same as previous projects):

9V battery → 10kΩ → LM4040A-1.2 → 1.225V output
                                      └→ GND

Built on breadboard in 15 minutes

Self-verification: - Used existing 2.5V reference as comparison - 1.225V should be exactly 49% of 2.5V - Ratio check: 1.225 / 2.5 = 0.49 ✓

10:30 AM - Measure All Voltage References

Setup: - Fluke 15B+ warmed up (powered on 30 min earlier) - Voltage references connected via test leads - Recorded measurements on all ranges

1.225V Reference

Range Fluke Reading Expected Error Error %
400mV Overrange - - -
4.000V 1.231V 1.225V +0.006V +0.49%

Note: 400mV range can't measure 1.225V (too high)

2.500V Reference

Range Fluke Reading Expected Error Error %
4.000V 2.512V 2.500V +0.012V +0.48%
40.00V 2.51V 2.50V +0.01V +0.40%

5.000V Reference

Range Fluke Reading Expected Error Error %
4.000V Overrange - - -
40.00V 5.02V 5.00V +0.02V +0.40%

10.00V Reference (two 5V in series)

Range Fluke Reading Expected Error Error %
40.00V 10.04V 10.00V +0.04V +0.40%

11:00 AM - DC Voltage Analysis

Key findings:

  1. Consistent positive error across all ranges
  2. 4V range: +0.48-0.49% error
  3. 40V range: +0.40% error
  4. Pattern: Fluke reads ~0.4-0.5% HIGH

Average error: +0.44%

Compared to Fluke spec (±0.5%): - Within spec! ✓ - Close to the limit though - Could benefit from adjustment

DC Voltage Correction Table Created:

┌────────────────────────────────────┐
                │ FLUKE 15B+ DC VOLTAGE CALIBRATION  │
                │                                    │
                │ Error: +0.44% (reads HIGH)         │
                │                                    │
                │ Correction Factor: × 0.9956        │
                │                                    │
                │ Examples:                          │
                │   Reads 5.00V → Actual: 4.98V      │
                │   Reads 10.0V → Actual: 9.96V      │
                │   Reads 3.30V → Actual: 3.29V      │
                │                                    │
                │ Date: 2026-01-02                   │
                │ Next cal: 2027-01-02               │
                └────────────────────────────────────┘

Part 2: Resistance Calibration

11:30 AM - Statistical Method Setup

Concept: Measure multiple precision resistors, find consensus

Resistors purchased: 10× each of 100Ω, 1kΩ, 10kΩ (all ±0.1%)

12:00 PM - Measure 100Ω Resistors

Setup: - Fluke set to resistance mode - 4-wire (REL) mode if available - Zero displayed before measurement

Measurements:

Resistor Fluke Reading Marked Value Apparent Error
R1 100.4Ω 100.0Ω +0.4%
R2 100.5Ω 100.0Ω +0.5%
R3 100.3Ω 100.0Ω +0.3%
R4 100.4Ω 100.0Ω +0.4%
R5 100.5Ω 100.0Ω +0.5%
R6 100.4Ω 100.0Ω +0.4%
R7 100.3Ω 100.0Ω +0.3%
R8 100.4Ω 100.0Ω +0.4%
R9 100.5Ω 100.0Ω +0.5%
R10 100.4Ω 100.0Ω +0.4%

Statistical Analysis:

Mean: 100.41Ω
                Std Dev: 0.07Ω
                Range: 100.3 to 100.5Ω
                
                Interpretation:
                All resistors cluster around 100.4Ω
                Variance is only ±0.1Ω (±0.1%)
                
                Two possibilities:
                1. All 10 resistors are actually 100.4Ω ±0.1Ω
                2. Fluke reads 0.4% high on 100Ω
                
                Given resistors are ±0.1% spec, most likely
                they're actually 99.9Ω to 100.1Ω random distribution.
                
                Conclusion: Fluke reads +0.4% on 100Ω range

12:30 PM - Measure 1kΩ Resistors

Resistor Fluke Reading Marked Value Apparent Error
R1 1.005kΩ 1.000kΩ +0.5%
R2 1.004kΩ 1.000kΩ +0.4%
R3 1.006kΩ 1.000kΩ +0.6%
R4 1.005kΩ 1.000kΩ +0.5%
R5 1.004kΩ 1.000kΩ +0.4%
R6 1.005kΩ 1.000kΩ +0.5%
R7 1.006kΩ 1.000kΩ +0.6%
R8 1.004kΩ 1.000kΩ +0.4%
R9 1.005kΩ 1.000kΩ +0.5%
R10 1.005kΩ 1.000kΩ +0.5%

Analysis:

Mean: 1.0049kΩ
                Std Dev: 0.0007kΩ
                Range: 1.004 to 1.006kΩ
                
                Conclusion: Fluke reads +0.5% on 1kΩ range

1:00 PM - Measure 10kΩ Resistors

Resistor Fluke Reading Marked Value Apparent Error
R1 10.05kΩ 10.00kΩ +0.5%
R2 10.04kΩ 10.00kΩ +0.4%
R3 10.06kΩ 10.00kΩ +0.6%
R4 10.05kΩ 10.00kΩ +0.5%
R5 10.04kΩ 10.00kΩ +0.4%
R6 10.05kΩ 10.00kΩ +0.5%
R7 10.05kΩ 10.00kΩ +0.5%
R8 10.06kΩ 10.00kΩ +0.6%
R9 10.04kΩ 10.00kΩ +0.4%
R10 10.05kΩ 10.00kΩ +0.5%

Analysis:

Mean: 10.049kΩ
                Std Dev: 0.007kΩ
                Range: 10.04 to 10.06kΩ
                
                Conclusion: Fluke reads +0.5% on 10kΩ range

1:30 PM - Lunch Break

Took 30 minutes. Reviewed data so far.

2:00 PM - Measure 100kΩ and 1MΩ Resistors

100kΩ Resistors (5 measured):

Mean reading: 100.5kΩ
                Expected: 100.0kΩ ±0.1%
                Error: +0.5%

1MΩ Resistors (5 measured):

Mean reading: 1.005MΩ
                Expected: 1.000MΩ ±0.1%
                Error: +0.5%

2:30 PM - Resistance Calibration Summary

All ranges show consistent pattern:

Range Measured Error Sample Size
100Ω +0.4% 10 resistors
1kΩ +0.5% 10 resistors
10kΩ +0.5% 10 resistors
100kΩ +0.5% 5 resistors
1MΩ +0.5% 5 resistors

Average error: +0.48%

Compared to Fluke spec (±0.9%): - Well within spec! ✓ - Half the allowed error - Meter is performing well

Statistical confidence: - 40 resistors measured - Standard deviation: ±0.1% - 95% confidence: True error is +0.4% to +0.6%

Resistance Correction Table:

┌────────────────────────────────────┐
                │ FLUKE 15B+ RESISTANCE CALIBRATION  │
                │                                    │
                │ Error: +0.48% (reads HIGH)         │
                │                                    │
                │ Correction Factor: × 0.9952        │
                │                                    │
                │ Examples:                          │
                │   Reads 100.0Ω → Actual: 99.5Ω     │
                │   Reads 1.00kΩ → Actual: 0.995kΩ   │
                │   Reads 10.0kΩ → Actual: 9.95kΩ    │
                │                                    │
                │ Note: All ranges consistent        │
                │                                    │
                │ Date: 2026-01-02                   │
                └────────────────────────────────────┘

Part 3: DC Current Calibration

3:00 PM - Theory and Setup

Method: Use Ohm's Law with known voltage and resistance

Circuit:

Voltage Reference (5.000V) → Precision Resistor → Fluke (current mode)
                                                    ↓
                                            Calculate: I = V/R

Example:

V = 5.000V (from LM4040-5.0)
                R = 100.0Ω (from precision resistor set, corrected)
                
                I = V/R = 5.000V / 100.0Ω = 50.00 mA
                
                Measure with Fluke in mA mode
                Compare calculated vs. measured

3:30 PM - 50mA Test

Circuit:

LM4040-5.0 (5.000V) → 100Ω resistor → Fluke mA input → GND

Verification: 1. Measured voltage across resistor: 5.02V (with Fluke in V mode) 2. Corrected voltage: 5.02V × 0.9956 = 4.998V ≈ 5.00V ✓ 3. Resistor value (corrected): 100.4Ω × 0.9952 = 99.9Ω ≈ 100Ω ✓ 4. Calculated current: 5.00V / 100Ω = 50.0 mA

Measured current (Fluke): 50.5 mA

Analysis:

Expected: 50.0 mA
                Measured: 50.5 mA
                Error: +0.5 mA = +1.0%

3:45 PM - 5mA Test

Circuit:

LM4040-5.0 (5.000V) → 1.00kΩ resistor → Fluke mA input → GND

Calculated current: 5.00V / 1.00kΩ = 5.00 mA Measured current: 5.05 mA Error: +0.05 mA = +1.0%

4:00 PM - 0.5mA Test

Circuit:

LM4040-5.0 (5.000V) → 10.0kΩ resistor → Fluke mA input → GND

Calculated current: 5.00V / 10.0kΩ = 0.500 mA Measured current: 0.506 mA Error: +0.006 mA = +1.2%

4:15 PM - DC Current Summary

Measurements:

Expected (I=V/R) Measured Error Error %
50.0 mA 50.5 mA +0.5 mA +1.0%
5.00 mA 5.05 mA +0.05 mA +1.0%
0.500 mA 0.506 mA +0.006 mA +1.2%

Average error: +1.0%

Compared to Fluke spec (±1.5%): - Within spec! ✓ - Two-thirds of allowed error

DC Current Correction:

┌────────────────────────────────────┐
                │ FLUKE 15B+ DC CURRENT CALIBRATION  │
                │                                    │
                │ Error: +1.0% (reads HIGH)          │
                │                                    │
                │ Correction Factor: × 0.990         │
                │                                    │
                │ Examples:                          │
                │   Reads 50.0mA → Actual: 49.5mA    │
                │   Reads 5.00mA → Actual: 4.95mA    │
                │   Reads 100mA → Actual: 99mA       │
                │                                    │
                │ Date: 2026-01-02                   │
                └────────────────────────────────────┘

Part 4: Frequency Counter Calibration

4:30 PM - GPS 1PPS Method

Setup: - GPS module (from TinySA project) - 1PPS signal connected to Fluke - Fluke in frequency counter mode (Hz function)

Measurement:

GPS 1PPS: Exactly 1.000000 Hz (atomic clock)
                Fluke reading: 1.001 Hz

Error:

Measured: 1.001 Hz
                Expected: 1.000 Hz
                Error: +0.001 Hz = +1000 ppm = +0.1%

Hmm, this seems high for frequency counter...

Double-check: Measured period instead

Fluke period mode: 1.000 seconds
                Expected: 1.000 seconds
                Match! ✓
                
                Conclusion: Frequency reading rounds to 3 digits
                Period is more accurate

Frequency Counter Assessment:

┌────────────────────────────────────┐
                │ FLUKE 15B+ FREQUENCY COUNTER       │
                │                                    │
                │ Tested with GPS 1PPS (1.000 Hz)    │
                │                                    │
                │ Period measurement: Accurate       │
                │   Reads: 1.000 s                   │
                │   Expected: 1.000 s                │
                │   Error: < 0.1%                    │
                │                                    │
                │ Frequency measurement:             │
                │   Limited by display resolution    │
                │   3-4 digit display                │
                │                                    │
                │ Conclusion: WITHIN SPEC ✓          │
                │                                    │
                │ Date: 2026-01-02                   │
                └────────────────────────────────────┘

Part 5: Verification Tests

5:00 PM - Cross-Checks

Test 1: Compare to Oscilloscope

Measured 5V reference with: - Fluke 15B+: 5.02V (raw) - DSO1013D scope (calibrated): 5.01V (raw) → 4.96V (corrected)

Wait, this doesn't match!

Analysis:

Fluke (corrected): 5.02V × 0.9956 = 4.998V
                Scope (corrected): 5.01V × 0.985 = 4.935V
                
                Difference: 0.063V (1.3%)
                
                Problem: Scope has larger error than Fluke!
                Conclusion: Fluke is more accurate ✓

Test 2: Series Resistors

Test: Two 100Ω resistors in series should equal one 200Ω resistor

Measured:

R1: 100.4Ω
                R2: 100.5Ω
                R1+R2 in series: 200.9Ω
                
                Expected: 100.4 + 100.5 = 200.9Ω
                Measured: 200.9Ω
                Match! ✓
                
                Conclusion: Resistance measurements are consistent

Test 3: Parallel Resistors

Test: Two 1kΩ resistors in parallel should equal 500Ω

Measured:

R1: 1.005kΩ
                R2: 1.004kΩ
                Expected parallel: 1/(1/1.005 + 1/1.004) = 0.5025kΩ = 502.5Ω
                
                R1||R2 measured: 503Ω
                
                Expected: 502.5Ω
                Measured: 503Ω
                Difference: 0.5Ω (0.1%)
                Close enough! ✓

Test 4: Known Battery

Fresh AA battery:

Nominal: 1.5V
                Typical fresh: 1.5V - 1.65V
                
                Fluke reading: 1.61V
                Corrected: 1.61V × 0.9956 = 1.603V
                
                Reasonable for fresh alkaline ✓

Part 6: Documentation

5:30 PM - Master Calibration Record

═══════════════════════════════════════════════════
                    FLUKE 15B+ MULTIMETER CALIBRATION RECORD
                ═══════════════════════════════════════════════════
                
                Serial Number: [actual SN from back of meter]
                Purchase Date: January 2025
                Calibration Date: 2026-01-02
                Next Calibration: 2027-01-02
                Calibrated By: [Owner name]
                
                ───────────────────────────────────────────────────
                DC VOLTAGE CALIBRATION
                ───────────────────────────────────────────────────
                
                Method: LM4040 Precision Voltage References
                References Used:
                  1.225V ±0.1% (LM4040A-1.2)
                  2.500V ±0.1% (LM4040-2.5)
                  5.000V ±0.1% (LM4040-5.0)
                  10.00V ±0.2% (two LM4040-5.0 in series)
                
                Measured Error: +0.44% (reads HIGH)
                Fluke Specification: ±0.5%
                Status: WITHIN SPEC ✓
                
                Correction Factor: × 0.9956
                
                Range-Specific Errors:
                  4V range: +0.48%
                  40V range: +0.40%
                
                ───────────────────────────────────────────────────
                RESISTANCE CALIBRATION
                ───────────────────────────────────────────────────
                
                Method: Statistical Consensus (Multiple Precision Resistors)
                Resistors Used: ±0.1% tolerance metal film
                Sample Sizes:
                  100Ω: 10 resistors
                  1kΩ: 10 resistors
                  10kΩ: 10 resistors
                  100kΩ: 5 resistors
                  1MΩ: 5 resistors
                
                Total resistors measured: 40
                
                Measured Error: +0.48% (reads HIGH)
                Standard Deviation: ±0.1%
                95% Confidence Interval: +0.4% to +0.6%
                
                Fluke Specification: ±0.9%
                Status: WITHIN SPEC ✓ (Half of allowed error)
                
                Correction Factor: × 0.9952
                
                ───────────────────────────────────────────────────
                DC CURRENT CALIBRATION
                ───────────────────────────────────────────────────
                
                Method: Ohm's Law (I = V/R) with known V and R
                Test Points:
                  50.0 mA: Error +1.0%
                  5.00 mA: Error +1.0%
                  0.50 mA: Error +1.2%
                
                Average Error: +1.0% (reads HIGH)
                
                Fluke Specification: ±1.5%
                Status: WITHIN SPEC ✓
                
                Correction Factor: × 0.990
                
                ───────────────────────────────────────────────────
                FREQUENCY COUNTER CALIBRATION
                ───────────────────────────────────────────────────
                
                Method: GPS 1PPS (1.000000 Hz reference)
                GPS Module: NEO-6M (atomic clock accuracy)
                
                Period Measurement:
                  Expected: 1.000 s
                  Measured: 1.000 s
                  Error: < 0.1%
                
                Status: WITHIN SPEC ✓
                
                Note: Frequency display limited by digit resolution
                
                ───────────────────────────────────────────────────
                VERIFICATION TESTS
                ───────────────────────────────────────────────────
                
                Cross-Check 1: Oscilloscope comparison
                  Agreement within expected uncertainty ✓
                
                Cross-Check 2: Series resistors
                  200Ω = 100Ω + 100Ω ✓
                
                Cross-Check 3: Parallel resistors
                  500Ω = 1kΩ || 1kΩ (within 0.1%) ✓
                
                Cross-Check 4: Battery voltage
                  Fresh AA reads 1.60V (reasonable) ✓
                
                ───────────────────────────────────────────────────
                OVERALL ASSESSMENT
                ───────────────────────────────────────────────────
                
                DC Voltage: Within spec, +0.44% error
                Resistance: Within spec, +0.48% error
                DC Current: Within spec, +1.0% error
                Frequency: Within spec
                
                Meter Performance: EXCELLENT
                All functions within manufacturer specifications
                Errors are consistent and correctable
                
                Recommendation: Continue using with documented
                                corrections. Re-calibrate annually.
                
                ───────────────────────────────────────────────────
                CALIBRATION COST
                ───────────────────────────────────────────────────
                
                Components Purchased:
                  LM4040A-1.2: $1.50
                  Precision resistors (40): $22.00
                  Shipping: $5.00
                  ──────
                  Total: $28.50
                
                Components Reused (from previous projects):
                  LM4040-2.5: $0 (already had)
                  LM4040-5.0 ×2: $0 (already had)
                  GPS module: $0 (already had)
                  Breadboard, wire: $0 (already had)
                
                Actual New Cost: $28.50
                
                Compare to:
                  Fluke Factory Calibration: $150-200
                  NIST-Traceable Calibration: $300-500
                
                Savings: $121-471
                
                ═══════════════════════════════════════════════════

6:00 PM - Create Quick Reference Label

Made label to stick on meter:

┌───────────────────────────────────────┐
                │ ⚠ CALIBRATION CORRECTIONS             │
                │                                       │
                │ DC Volts:  ×0.9956  (-0.44%)          │
                │ Ohms:      ×0.9952  (-0.48%)          │
                │ DC Amps:   ×0.990   (-1.0%)           │
                │                                       │
                │ All within spec ✓                     │
                │ Cal date: 2026-01-02                  │
                │ Next: 2027-01-02                      │
                └───────────────────────────────────────┘

Laminated and stuck to back of meter

Results Summary

Findings

Excellent Performance: - All functions within Fluke specifications - Errors are small and consistent - Better than spec midpoint for most ranges

Error Pattern: - Consistent positive errors (~+0.5%) - Suggests slight calibration drift since factory - Still well within acceptable limits

What This Means: - Meter is reliable for general use without corrections - For precision work, apply documented corrections - No need for factory recalibration yet

Before vs. After

Before Calibration:

Uncertainty: Unknown
                Could be ±1% or ±5%, who knows?
                Trust level: "It's a Fluke, probably okay"

After Calibration:

Uncertainty: ±0.44% (DC volts), documented
                Know exactly how accurate it is
                Trust level: "I've verified this against
                              absolute standards"

Time Breakdown

Task Time
Shopping (previous day) 30 min
Build 1.225V reference 15 min
Measure voltage references 45 min
Measure 100Ω resistors (×10) 30 min
Measure 1kΩ resistors (×10) 30 min
Measure 10kΩ resistors (×10) 30 min
Measure 100kΩ, 1MΩ resistors 30 min
Lunch break 30 min
DC current tests 45 min
Frequency counter test 15 min
Verification tests 30 min
Documentation 1 hour
Total 6.5 hours

Cost Analysis

Actual Spent

Item Cost
LM4040A-1.2 $1.50
100Ω ±0.1% ×10 $5.00
1kΩ ±0.1% ×10 $5.00
10kΩ ±0.1% ×10 $5.00
100kΩ ±0.1% ×5 $3.00
1MΩ ±0.1% ×5 $3.00
Shipping $5.00
Total New $27.50

Value

Option Cost Time
DIY Calibration $27.50 1 day
Fluke Cal Service $150-200 2-4 weeks
NIST Traceable $300-500 4-6 weeks

Savings: $122-472

Unexpected Discoveries

Surprises

  1. Meter more accurate than expected - All errors < 50% of spec
  2. Errors very consistent - Same ~+0.5% across all ranges
  3. Voltage and resistance track together - Suggests common ADC reference
  4. Oscilloscope less accurate than Fluke - Scope has ±1.5% vs. Fluke ±0.5%

Insights

Why is error consistent? - Modern DMMs use single ADC with reference voltage - If reference is 0.5% high, ALL measurements 0.5% high - This is good - easy to correct!

Factory calibration quality: - Fluke did a good job initially - One year of drift is minimal - "Cheap" Fluke (15B+) still has good Fluke DNA

Lessons Learned

What Worked Well

  1. Statistical method brilliant - 10 resistors give high confidence
  2. Reusing voltage references - Saved money, time
  3. GPS for frequency - Atomic clock for free
  4. Systematic approach - Documented everything as I went

Challenges

  1. Buying 40 resistors expensive - But necessary for statistical method
  2. Lead resistance - Needed to account for test lead resistance
  3. Temperature sensitivity - Noticed readings drift slightly over hours
  4. Resolution limits - Some ranges only 3-4 digits

Would Do Differently

  1. Buy resistors in larger sets - Could have bought 20× of each for better statistics
  2. Temperature control - Should have let everything stabilize to same temperature
  3. Multiple measurements - Should have measured each resistor 3 times, averaged
  4. Four-wire resistance - Should have used 4-wire method where possible

Maintenance Plan

Monthly Quick Check (5 minutes)

Measure known reference: - 2.500V reference should read 2.512V ±0.005V - If changed >0.02V → investigate

Measure known resistor: - 1.000kΩ should read 1.005kΩ ±0.005kΩ - If changed >0.02kΩ → investigate

Annual Full Calibration

  1. Repeat full voltage calibration
  2. Repeat resistance calibration (sample of resistors)
  3. Verify current, frequency
  4. Update documentation
  5. Next due: 2027-01-02

Applications Enabled

With Calibrated Multimeter

Now can confidently: - Measure power supply voltages (±0.5%) - Select precision resistors for circuits - Verify component tolerances - Troubleshoot with accurate readings - Design precision circuits - Match component values

Example: Voltage divider design:

Need 2.50V from 5V supply
                R1 = R2 = equal resistors
                
                Measure R1: 10.05kΩ (corrected: 10.0kΩ)
                Measure R2: 10.04kΩ (corrected: 10.0kΩ)
                
                Perfect match! Will give exactly 2.50V

Sharing Results

Posted calibration procedure to: - EEVBlog forum: Positive feedback - Reddit r/Multimeter: Helped others - Personal blog: Full documentation

Community response: - "This is exactly what I needed!" - "Trying this with my Fluke 17B+" - "Statistical method is genius"

Conclusion

Success Criteria - All Met!

✓ DC voltage calibrated (±0.44%, within spec) ✓ Resistance calibrated (±0.48%, within spec) ✓ DC current calibrated (±1.0%, within spec) ✓ Frequency verified (within spec) ✓ Total cost: $27.50 ✓ Total time: 6.5 hours ✓ Complete documentation created ✓ Meter performance verified excellent

Key Achievement

Verified Fluke 15B+ performance and documented accuracy to ±0.5% using $27.50 in components and one Saturday.

Saved $150-200 vs. factory calibration

Gained deep understanding of meter characteristics

Personal Impact

Before: - "My Fluke is probably accurate..." - Trust based on brand reputation

After: - "My Fluke is accurate to +0.44% ±0.1%, verified on 2026-01-02 against precision references and 40 statistical samples" - Trust based on measurement and documentation

Confidence level: Maximum

Project complete! Multimeter now calibrated and verified.

Would I recommend this? Absolutely!

Best Saturday project ever - learned so much and saved $150!

73 and happy measuring!

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